Reinforced networked polymer/clay alloy composite

ABSTRACT

A reinforced networked polymer/clay alloy composite is produced by contacting a monomer/clay mixture with a reinforcing agent. The monomer/clay mixture comprises a monomer, a cross-linking agent and clay particles. An initiator means is used to initiate polymerization of the monomer/clay mixture, while the cross-linking agent concurrently acts to network oligomeric and polymeric species formed during polymerization to produce a networked polymer/clay alloy in the presence of the reinforcing agent. The networked polymer/clay alloy is intimately integrated with the reinforcing agent such that, on exposure to water, the networked polymer/clay alloy swells with substantially no clay separating from the composite.

This application is a continuation of U.S. patent application Ser. No.09/579,701 filed in the names of Zhihong Zhou, John Donald Payzant andWalter van Woudenberg on May 26, 2000, now U.S. Pat. No. 6,610,781 B1,which is a continuation-in-part of U.S. patent application Ser. No.09/356,278, filed Jul. 16, 1999, abandoned.

FIELD OF THE INVENTION

The present invention relates to absorbent materials. More specifically,the invention relates to a reinforced networked polymer/clay alloycomposite useful, for example, in containment applications such aslandfill liners or covers, reservoir liners, underground storage tankliners, secondary containment liners, and man-made bodies of water, orpersonal care absorbent articles, including diapers, training pants,feminine hygiene products such as sanitary napkins, incontinence devicesand the like.

BACKGROUND DISCUSSION

There are a number of commercial applications for absorbent materials,including, without limitation, in containment applications as landfillliners or covers, reservoir liners, underground storage tank liners,secondary containment liners, and man-made bodies of water, or personalcare absorbent articles, including diapers, training pants, femininehygiene products such as sanitary napkins, incontinence devices and thelike. While the applications are diverse, there is need for a materialhaving improved water absorbency and/or fluid barrier properties.

For example, in waste containment applications, hydraulic barriers canreduce the escape or leakage of harmful leachates into surface andground waters. In man-made bodies of water, a hydraulic barrier acts tocontain the water within an enclosure or defined impoundment area.

In one type of liner, hydraulic barriers are often formed frombentonite. Specifically, bentonite is admixed with the soil forming thewater-holding area. Upon contact of the bentonite with water, thebentonite swells and thereby fills up the voids found in the soil.However, the water absorption capacity of bentonite alone may not besufficient for the containment of some water-soluble wastes.

U.S. Pat. No. 3,949,560 (Clem, Apr. 13, 1976) is directed to a soilsealant composition dry mixed with soil. The soil sealant compositionconsists of bentonite, a water-soluble dispersing agent and a pre-formedwater-soluble polymer. The water-soluble dispersing agent is aphosphoric acid salt, sulfate of ROSO₃X (R is a C₈-C₃₂ hydrocarbon, X isan alkaline metal or ammonium) or a leonardite salt. The pre-formedwater-soluble polymer is polyacrylic acid, water-soluble salts ofpolyacrylic acid, hydrolyzed poly-acrylonitrile, polyvinyl acetate,polyvinyl alcohol, copolymers of the foregoing or a copolymer of acrylicacid and maleic anhydride. A water containing enclosure is formed fromthe soil/soil sealant mixture and contacted with water to hydrate thebentonite. The resulting hydrated enclosure is used for containing watercontaminated with industrial waste. No reinforcing agent is used withthe soil/soil sealant mixture.

U.S. Pat. No. 4,048,373 (Clem, Sep. 13, 1977), U.S. Pat. No. 4,103,499(Clem, Aug. 1, 1978) and U.S. Pat. No. 4,139,588 (Clem, Feb. 13, 1979)all describe a water barrier panel or moisture impervious panelcomprised of a soil sealant sandwiched between two paperboard sheets.More particularly, the panel is formed of a corrugated paperboardcarrier or form including a pair of spaced paperboard facing sheetsinterconnected by a paper corrugated strip to form a plurality of voids.The voids are filled with the soil sealant composition described in U.S.Pat. No. 3,949,560 and the edges of the panel may be sealed with wax,tape or water-soluble gum. When contacted with water, moisture passesthrough the paperboard sheets to the soil sealant composition, where thebentonite swells.

More recently, so-called geosynthetic clay liners (“GCL”) have becomerelatively widely accepted for use as hydraulic barriers. A GCL has alayer of bentonite supported by a geotextile or a geomembrane material,mechanically held together by needling, stitching or chemical adhesives.

An example of a GCL prepared with a chemical adhesive is provided inU.S. Pat. No. 4,467,015 (Clem, Aug. 21, 1984). This patent describes awaterproofing structure or water impervious sheet material comprised oflayers of flexible carrier sheets coated with a water swellablecomposition. The water swellable composition is clay or a dry granularmixture of clay, a pre-formed water-soluble polymer, such as polyacrylicacid, and a water-soluble salt. The composition is secured by using anadhesive, whether water-soluble or -insoluble or a solvent-soluble or-insoluble adhesive. A disadvantage of this type of laminate is thatclays in the GCL may still migrate away from the GCL with the leachatepercolating through the liner, albeit very slowly.

Similarly, U.S. Pat. No. 4,810,573 (Harriet, Mar. 7, 1989) describes alaminated composite article with a clay composition adhered to awater-impermeable sheet. The clay composition is an intimate mixture ofwater swellable clay and a pre-formed elastomer, such as polypropyleneand/or polybutene. The intimate clay/elastomer mixture is produced byblending clay with pre-formed elastomers in a sigma blender to masticatethe elastomer. The clay composition is adhered to the water-impermeablesheet by rolling to form a laminate. U.S. Pat. No. 5,580,630 (Byrd, Dec.3, 1996) describes a multi-layer article using the same clay compositionas Harriet.

As indicated above, rather than using a chemical adhesive, the layers ofthe GCL may be mechanically held together by other means such asstitching and needle punching. For instance, U.S. Pat. No. 4,565,468(Crawford, Jan. 21, 1986) described a moisture impermeable barriercomprised of two fabric layers quilted together. A top sheet member ispositioned over a base sheet member having a layer of bentonite restingon its upper surface. The top sheet member is secured to the base sheetmember by stitches extending therebetween. The stitching forms eitherquilted compartments or elongated corrugated compartments containing thebentonite therein.

DE 3704503 A1 (Heerten et al.) discloses an article having two fabriclayers sandwiching a bentonite clay layer, wherein the two fabric layersare needle punched together. U.S. Pat. No. 5,174,231 (White, Dec. 29,1992) describes a multi-layer article including an intermediate layer ofa water-swellable colloidal clay sandwiched between two layers offlexible material or fabric sheet. The two layers are structurallyinterconnected through the intermediate clay layer, such as by needlepunching, sewing, quilting, or needle looming, to interconnect fibers ofone fabric layer to the other fabric layer at spaced locations overessentially the entire surface areas of both layers.

Thus, in these GCLs, the clay particles are either adhered onto thegeotextile or geomembrane or are physically confined by opposing layersof geotextile or geomembrane. The opposing layers of geotextile orgeomembranes are mechanically held together by means such as sewing,quilting and needle punching, which limits the movement of clayparticles therebetween. However, the clay particles in granularbentonite used in these applications are typically a couple ofmicrometers or less in diameter. Further, the void spaces in thegeotextiles or geomembranes and the spacing of the stitching or needlepunching tend to be greater than the size of the clay articles. Thus, itis still possible for the clay particles in the GCL to migrate out ofthe liner, particularly when placed under a hydraulic pressure gradient,albeit slowly.

It is commonly known that bentonite swells well in fresh water butpoorly in, water containing salts and/or metals, such as saltwater,seawater, acid mine drainage, and the like. Thus, while GCL's areeffective barriers for fresh water, they are ineffective barriers towater with high salt and dissolved metals concentrations.

Another problem with GCL's is that the bentonite is typically dry and,therefore, until the bentonite swells, waste water can flow through theGCL. Accordingly, GCL's must first be pre-hydrated after installation.This pre-hydration step can take up to 48 hours, for example.

Yet another problem with GCL's is their weight. Typically, a GCL weighsmore than 5 kg/m². Because of its weight, transportation andinstallation costs are significant.

Accordingly, there is a need for an absorbent material for containmentapplications, especially environmental containment applications, whichis salt water and contaminant resistant. Also, there is a need for abarrier liner that is lighter than GCL, but having substantiallycomparable or improved barrier properties versus GCL. Moreover, there isa need for an absorbent material having intimately integrated componentsthat do not disperse and/or migrate from the product, particularly whenexposed to or immersed in water, and can effectively absorb watercontaining salt and/or metals.

SUMMARY OF THE INVENTION

According to the invention, there is provided a reinforced networkedpolymer/clay alloy composite comprising a networked polymer/clay alloy,wherein the alloy is a chemically integrated composition of polymer andclay, and the alloy is intimately integrated with a reinforcing agent sothat, when the composite is immersed in deionized water, at atemperature in a range of from about 20° C. to about 30° C., the alloyswells with substantially no clay separating from the composite.

According to the invention, there is provided the method of using thereinforced networked polymer/clay alloy composite as an absorbentmaterial for a personal care product or as a fluid barrier in aconfining stress range of from about 0 kPa to about 10000 kPa, wherein,when placed under a zero confining stress, the barrier has a deionizedwater flux less than about 1×10⁻⁸ m³/m²/s.

BRIEF DESCRIPTION OF THE DRAWINGS

The reinforced networked polymer/clay alloy composite and the processfor producing the reinforced networked polymer/clay alloy composite ofthe present invention will be better understood by referring to thefollowing detailed description of preferred embodiments and the drawingsreferenced therein, in which:

FIG. 1 is a schematic of one embodiment of an apparatus for use inproducing one embodiment of the reinforced networked polymer/clay alloycomposite;

FIG. 2 is a schematic of another embodiment of an apparatus for use inproducing one embodiment of the reinforced networked polymer/clay alloycomposite;

FIG. 3 is a schematic of a further embodiment of an apparatus for use inproducing one embodiment of the reinforced networked polymer/clay alloycomposite;

FIG. 4 is a graphical representation of the results of the flux test inExample 6 for 3.5% (wt.) NaCl solution and the minimum flux forconventional GCL under similar salt water conditions indicated by thedotted line;

FIG. 5 is a graphical representation of the results of the flux test inExample 6 for artificial seawater and the minimum flux for conventionalGCL under similar salt water conditions indicated by the dotted line;

FIG. 6 is a scanning electron microscope (SEM) micrograph of a top planperspective of the reinforcing agent used in Example 7, at amagnification of 140×;

FIG. 7 is an SEM micrograph of a hydrated polymer used for comparison inExample 7, at a magnification of 7000×;

FIG. 8 is an SEM micrograph of a cross-section of a reinforced networkedpolymer/clay alloy composite produced in Example 7, at a magnificationof 50×;

FIG. 9 is an SEM micrograph of a cross-section of a reinforced networkedpolymer/clay alloy composite produced in Example 7, at a magnificationof 270×;

FIG. 10 is an SEM micrograph of a cross-section of a water-swelledreinforced networked polymer/clay alloy composite produced in Example 7,at a magnification of 500×;

FIG. 11 is an SEM micrograph of a cross-section of a water-swelledreinforced networked polymer/clay alloy composite produced in Example 7,at a magnification of 4500×;

FIG. 12 is an SEM micrograph of a cross-section of a water-swelledpolymer, without clay, at a magnification of 650×;

FIGS. 13A and 13B are drawings based on photographs taken of Sample A inExample 8 prior to immersion (13A) and after 3 hours immersion indeionized water (13B);

FIGS. 14A and 14B are drawings based on photographs taken of Sample D inExample 8 prior to immersion (14A) and after 3 hours immersion indeionized water (14B); and

FIGS. 15A and 15B are drawings based on photographs taken of Sample G inExample 8 prior to immersion (15A) and after 3 hours immersion indeionized water (15B).

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Definitions

“Monomer” is an organic molecule that can combine with a number of thesame or different molecules to form a large molecule having repeatingmonomeric units, wherein the repeating monomeric units have a similarchemical architecture and atom composition as the monomeric units.

“Polymer” is a large molecule built from the same or different repeatingmonomeric units and typically has a molecular weight in a range fromabout 10,000 to about 20,000,000. Polymer, as used herein, also includesany polymer made from two or more different repeating units, such ascopolymers (i.e., comprising two different monomeric units), terpolymers(i.e., comprising three different monomeric units), tetrapolymers (i.e.,comprising four different monomeric units) and so on. Moreover, therepeating monomeric units can alternate in a sequential pattern (e.g.,A-B-A-B), block pattern (e.g., A-A-B-B), random pattern (A-B-B-A-B-A) orcombinations thereof.

“Oligomer” is also built from the same or different repeating monomerunits but is a smaller molecule than a polymer and typically has amolecular weight in a range of from about 200 up to about 9,000.

“Polymerization Initiator Means” is a chemical substance, gamma rayirradiation, X-ray irradiation, irradiation by high energy sub-atomicparticles, each type of radiation having a wavelength less than about 10nm, (collectively, high energy irradiation) and combinations thereofthat can increase the reactivity of a monomer so that a polymerizationor oligomerization chain reaction between monomers is initiated and apolymer or oligomer is formed. At the appropriate temperature, certainchemical substances become either an ionic or free radical species thatcan react with a monomer alone to produce an ionic or free radicalmonomeric species, which can, in turn, react with another monomer,thereby initiating a polymerization reaction. Also, high energyirradiation can be used to produce an ionic or free radical monomericspecies from a monomer and/or a chemical substance other than a monomerto initiate a polymerization reaction.

“Cross-linking Agent” is a chemical substance, photons produced from aradiation source and combinations thereof that assist in forming abridging moiety between two or more backbone structures formed bymultiple monomeric units (e.g., oligomeric or polymeric units). Thus, across-linking agent can bridge oligomeric or polymeric species eitherduring or after their formation.

“Networked Polymer” is a very large polymer molecule formed bycross-linking multiple oligomers and/or polymers to form aninterconnected polymeric network. A networked polymer can havecross-linking moieties between oligomers and/or polymers, where themoieties are formed from either the cross-linking agent itself, branchesattached to the backbone of each oligomer and/or polymer or combinationsthereof.

“Networked Polymer/Clay Alloy” (“NPC Alloy”) is a chemically integratedcomposition of polymer and clay. Clay particles form a unique chemicalassociation with the networked polymer as it is formed. The chemicalassociation may be, for example, without limitation, through hydrogenbonding, ionic bonding, Van der Waal's/dipole bonding, affinity bonding,covalent bonding and combinations thereof.

“Reinforcing Agent” is a material having a sufficiently porous orpermeable structure so that a networked polymer, and/or an NPC alloy canform around and/or in the material's structure, thereby providingadditional support and/or strength to the aforementioned networkedpolymer or polymer/clay compositions.

“Reinforced Networked Polymer/Clay Alloy Composite” (“Reinforced NPCAlloy Composite”) is a macroscopic combination comprising a reinforcingagent and an NPC alloy. There is an intimate three-dimensionalintegrated association between composite components, as opposed to asimple two-dimensional laminate composite, where there is no integrationalong a third dimension.

General Discussion

A reinforced NPC alloy composite of the present invention is anabsorbent material useful, for example, without limitation, incontainment applications such as landfill liners or covers, reservoirliners, underground storage tank liners, secondary containment liners,and liners for man-made bodies of water, or personal care absorbentarticles, including diapers, training pants, feminine hygiene productssuch as sanitary napkins, incontinence devices and the like.

In containment applications, the composite material preferably absorbswater to form a barrier, which then has a relatively low permeability towater, oil and other liquids. In personal care articles, the compositematerial preferably has a high water absorbency capacity. As discussedmore fully below, the properties of the reinforced NPC alloy compositecan be adjusted depending on the application.

The reinforced NPC alloy composite of the present invention has improvedresistance to chemical, electromagnetic radiation and biologicaldegradation in surface and subsurface conditions. By improved resistanceto chemical degradation, we mean that the composite has improvedresistance to, for example, without limitation, salt water and drainagefluids with high heavy metal content and/or acidic pH. By improvedresistance to electromagnetic degradation, we mean that the compositehas an improved resistance to ultraviolet (UV) and other potentiallydetrimental electromagnetic radiation. By improved resistance tobiological degradation, we mean that the NPC alloy would be moreresistant to bacterial attack after installation, as compared with apolymer without clay.

For example, the permeability of a liner produced with the reinforcedNPC alloy composite is not significantly affected by salt water, orother aqueous solutions with heavy metals and/or acidic pH. Thus, thecomposite represents an improvement over a conventional GCL liner, whichtypically loses its effectiveness on exposure to salt water.

As another example, polyacrylamide is stable at surface and sub-surfaceconditions. However, it is susceptible to chemical and UV degradation.The clay reduces degradation in the NPC alloy by protecting the polymer.Also, the NPC alloy is more resistant to biological degradation than,for example, polyacrylic acid alone.

When used in barrier applications, the reinforced NPC alloy compositeweighs less than a conventional GCL per unit area. Also, the reinforcedNPC alloy composite can be used without pre-hydration, as is oftenrequired for conventional GCL's.

A reinforced NPC alloy composite is produced by intimately distributinga mixture of monomer, clay particles, a cross-linking agent and a mixingfluid (i.e., an MCX mixture) in, on and/or among a reinforcing agent,such as a porous substrate or non-aggregated fibers. By “intimatelydistributing”, “intimate distribution” or “intimately distributed”, wemean that an MCX mixture is distributed throughout the porous substrateor non-aggregated fibers so that a substantial portion of the surfaces,voids and interstitial spaces of and/or between the fibers or substrateis covered and/or occupied with the MCX mixture. Preferably, the MCXmixture is intimately distributed substantially through the thickness ofthe reinforcing agent.

After the MCX mixture is intimately distributed in, on and/or among thereinforcing agent, the MCX mixture is polymerized. The clay particlesare chemically associated with the networked polymer as it is formed toproduce an NPC alloy. Because of the intimate MCX mixture distribution,the NPC alloy is intimately integrated with the reinforcing agent.

The polymer and clay in the NPC alloy cooperate physically andchemically (i.e., physicochemically) to contribute to the reinforced NPCalloy composite's water absorbency. Thus, the composite can swellsubstantially as an integrated unit while only negligible amounts ofclay, if any, (i.e., substantially no clay) separate from the compositewhen it is immersed in deionized water at temperatures in a range offrom about 1° C. to about 60° C.

Monomer/Clay Mixture

The monomer/clay mixture used in making the NPC alloy includes, withoutlimitation, a monomer, clay particles, a cross-linking agent and amixing fluid. For brevity, we may refer to the mixture of monomer, clay,cross-linking agent and mixing fluid as “MCX.”

The monomer is at least partially soluble in the mixing fluid. A monomersoluble in the mixing fluid may be mixed with other monomers that aresoluble or insoluble in the mixing fluid. Preferably, at least onewater-soluble monomer has the following general formula:

wherein X is selected from the group consisting of OM, OR⁴ and NR⁵R⁶, Mis an alkali or alkaline earth metal ion or NH₄ ⁺, R¹, R², R³, R⁵, R⁶and R⁷ are independently selected from the group consisting of H, CH₃,CH₂CH₃, CH₂CH₂CH₃, CH(CH₃)₂, CH₂CH₂CH₂CH₃, and CN, and OR⁴ is selectedfrom the group consisting of OH, OCH₃, OCH₂CH₃, OCH₂CH₂CH₃, OCH(CH₃)₂,OCH₂CH₂CH₂CH₃, OCH₂CH₂OH and (OCH₂CH₂)_(m)OH, n=0 to about 10 and m=1 toabout 10.

More preferably, the monomer is selected from the group consisting ofacrylic acid (where R¹=H, R²=H, R³=H, n=0, X=OR⁴, R⁴=H), acrylamide(where R¹=H, R²=H, R³=H, n=0, X=NR⁵R⁶, R⁵=H, R⁶=H), sodium acrylate(where R¹=H, R²=H, R³=H, n=0, X=OM, M=Na), potassium acrylate (whereR¹=H, R²=H, R³=H, n=0, X=OM, M=K), methacrylic acid (where R¹=H, R²=H,R³=CH₃, n=0, X=OR⁴, R⁴=H), N-isopropylacrylamide (where R¹=H, R²=H,R³=H, n=0, X=NR⁵R⁶, R⁵=CH(CH₃)₂, R⁶=H), and combinations thereof.

An example of a monomer that can be co-polymerized with a monomer of theabove general formula are vinyl esters, such as vinyl acetate. Vinylacetate is readily co-polymerized and may be retained as a vinyl acetatemoiety or subsequently hydrolyzed to the corresponding vinyl alcohol.

The clay particles may be swelling or non-swelling clays. Suitableswelling clay particles include, without limitation, montmorillonite,saponite, nontronite, laponite, beidellite, iron-saponite, hectorite,sauconite, stevensite, vermiculite, and combinations thereof. Suitablenon-swelling clay particles include, without limitation, kaolin minerals(including kaolinite, dickite and nacrite), serpentine minerals, micaminerals (including illite), chlorite minerals, sepiolite, palygorskite,bauxite, silica and combinations thereof.

Preferably, the clay is a swelling clay such as, for example, smectiteand vermiculite type clays. More preferably, the clay is a smectite typeclay. Examples of suitable smectites are, without limitation,montmorillonite (sometimes referred to as bentonite), beidellite,nontronite, hectorite, saponite, sauconite and laponite. Bentonite is anexample of a naturally-occurring combination of clay particles.Bentonite is a rock rich in montmorillonite and may also comprise othersmectites as well as other non-clay mineral constituents. Consequently,montmorillonites or their mixtures with other smectites are oftenreferred to simply as bentonite. Bentonite clays are fine crystals orparticles, usually plate-like in shape, with a lateral dimension up to 2μm and a thickness in a range of a few to tens of nanometers (nm).

Swelling clays have the ability to absorb water and are less expensivethan monomer. Accordingly, the reinforced networked polymer composite ofthe present invention is less expensive than one produced without clay.Moreover, clay particles are resistant to degradation in long-termenvironmental applications, while still providing water absorbency forlong periods of time.

Non-swelling clays would provide increased resistance to salt water forthe reinforced NPC alloy composite. Also, non-swelling clays, likeswelling clays, are less expensive than monomer and would reduce thecomposite's cost.

Preferably, the weight ratio of clay to monomer in the MCX mixture is ina range of from about 0.05:1 to about 19:1. More preferably, the weightratio of clay to monomer in the MCX mixture is in a range of from about0.5:1 to about 3:1.

Suitable chemical substances for use as cross-linking agents include,without limitation, N,N′-methylene bisacrylamide, phenol formaldehyde,terephthalaldehyde, allylmethacrylate, diethyleneglycol diacrylate,ethoxylated trimethylolpropane triacrylate, ethylene carbonate, ethyleneglycol diglycidal ether, tetraallyloxyethane, triallylamine,trimethylolpropanetriacrylate, and combinations thereof.

As a general rule, depending on the selected polymerization reactiontime and temperature, a higher ratio of cross-linking agent to monomerwill generally produce a lower concentration of residual monomer, butthe networked polymer's water absorption capacity (WAC) may drop if theratio gets too high. The weight ratio of the cross-linking agent to themonomer is preferably in a range of from about 0.05:100 to about1.5:100. More preferably, the weight ratio of the cross-linking agent tothe monomer is in a range of from about 0.05:100 to about 0.7:100. Mostpreferably, the weight ratio of the cross-linking agent to the monomeris in a range of from about 0.1:100 to about 0.5:100.

The mixing fluid is a polar solvent. Examples of suitable mixing fluidsinclude, without limitation, water, alcohol, oxygen-containing organicsolvents, and combinations thereof, in which the monomer can be at leastpartially dissolved. Examples of suitable oxygen-containing organicsolvents include, without limitation, alcohols, glycols, polyols,sulfoxides, sulfones, ketones and combinations thereof. Preferably, themixing fluid is water, alcohol or a combination thereof. Mostpreferably, the mixing fluid is water.

Preferably, the amount of mixing fluid in the MCX mixture is in a rangeof from about 30% to about 90% by weight. More preferably, the amount ofmixing fluid in the MCX mixture is in a range of from about 40% to about80% by weight. Most preferably, the amount of mixing fluid in the MCXmixture is in a range of from about 40% to about 60% by weight.

Additionally, the MCX mixture preferably comprises one or moreadditives. Buffering agents and/or neutralizing agents may be used asadditives to maintain the pH of the mixture in a predetermined rangeand/or neutralize acidic and/or basic monomers.

Also, metal complexing agents may be used as additives to form metalcomplexes, thereby sequestering metal ions that might otherwiseinterfere with forming the NPC alloy. For example, acrylamide monomer istypically manufactured with cupric salts as a stabilizer (e.g., toinhibit polymerization during shipment or in storage). Thus, a metalcomplexing agent, such as a sodium carbonate orethylenediaminetetracetic acid (EDTA), can be added to the MCX mixtureto complex the metal ion and thereby sequester the metal. It should beunderstood that some additives can be used to satisfy multiplefunctions. For example, sodium carbonate (Na₂CO₃) and sodium bicarbonate(NaHCO₃), could function as both a buffering agent (i.e., maintainingpH) and a neutralizing agent (i.e., neutralizing acidic monomers), whilealso working as a metal complexing agent. Therefore, it will be apparentto those skilled in the art that one or more additives can be used forforming an NPC alloy depending on the monomer and cross-linking agentused, type of stabilizing agent mixed with the monomer, type ofpolymerization reaction and the desired reaction pH and temperature.

Examples of buffering agents and/or neutralizing agents include, withoutlimitation, sodium hydroxide, potassium hydroxide, ammonium hydroxide,sodium carbonate, sodium bicarbonate, potassium carbonate, potassiumbicarbonate, oxylate-containing compounds, sulfate-containing compounds,phosphate-containing compounds, and combinations thereof.

Examples of metal complexing agents include, without limitation, sodiumcarbonate, sodium bicarbonate, potassium carbonate, potassiumbicarbonate, ethylenediaminetetraacetic acid (EDTA), EDTA salts,orthophosphate, pyrophosphate, metaphosphate, hydrogen phosphate, andcombinations thereof.

Each of the components of the MCX mixture may be added in any order.Preferably, however, the mixing fluid and monomer are mixed with anyother desired component, followed by adding a chemical initiator andthen adding the clay. Also, caution should be exercised in mixing anymixture components to avoid any significant exotherms. Otherwise, anysignificant exotherm should be allowed to cool. A large exotherm frommixing components might otherwise lead to premature polymerizationshortly after the initiator is added, but before the mixture isintimately distributed in, on and/or among the reinforcing agent andheated under a controlled condition.

The MCX mixture forms a slurry type mixture, which should be mixed untilit is substantially homogeneous.

Reinforcing Agent

The reinforcing agent may comprise non-aggregated fibers or a substratehaving a porous structure. Examples of porous substrates includeknitted, woven and non-woven, natural and synthetic fibers. Suitablesynthetic fibers for either type of reinforcing agent include, forexample, without limitation, polypropylene, polyester, polyamide,polyethylene fibers, and combinations thereof. Examples of suitablenatural fibers include, without limitation, wood pulp, cotton, hemp,flax and asbestos fibers, and combinations thereof.

Preferred porous substrates for landfill applications include geotextilematerials. Examples of suitable non-woven geotextiles are, withoutlimitation, PETROMAT™ 4597 (Amoco), AMOCO 4551™, AMOCO 4553™, AMOCO4506™, GEOTEX® (Synthetic Industries, Inc., Chattanooga, Tenn., U.S.A.)and TERRAFIX® 270R-A (Terrafix Geosynthetics Inc., Toronto, Ontario,Canada). Preferred geotextiles have a unit weight in a range of fromabout 0.1 to 0.8 kg/m².

Another preferred porous substrate is a geotextile bonded to ageomembrane. Presently, one type of geotextile-geomembrane laminate iscommercially available from Vernon Plastics, Haverhill, Mass., USA.

Alternatively, the geotextile-geomembrane laminate could be formed in acontinuous process by bonding a geomembrane material to a geotextile.For example, without limitation, suitable geomembrane materials are highdensity polyethylene (HDPE), polyvinyl chloride (PVC), very flexiblepolyethylene (VFPE), flexible polypropylene (fPP), chlorosulfonatedpolyethylene (CSPE), and combinations thereof. The geomembrane may bebonded to the geotextile, for example, without limitation, by heat,adhesive, and combinations thereof.

The geomembrane material can be applied to the porous substrate materialeither before or after the substrate material is mixed with thepolymer/clay alloy mixture to form the NPC alloy composite. Preferably,however, the polymer/clay alloy mixture is dispersed in the substratematerial using a roller or piston.

The use of a geotextile-geomembrane laminate as a reinforcing agent isparticularly advantageous in some applications, for example land-fillapplications, where it is desired to use both a primary liner (often ageomembrane) and a secondary liner (for example, a GCL). By using ageotextile-geomembrane laminate as a reinforcing agent, a reinforced NPCalloy composite can be installed in one step.

In certain applications, for example, as landfill liners and covers, itmay be desirable to use a reinforcing agent that is resistant tobiodegradation. In other applications, for example, personal careabsorbent articles, it may be desirable to use a reinforcing agent thatwill biodegrade within a selected time period.

Whether the reinforcing agent is a porous substrate or non-aggregatedfibers, the inventive process produces a non-laminated, but intimatelyintegrated, composite between the reinforcing agent and the NPC alloy.Preferably, the reinforcing agent is dispersed homogeneously throughoutthe NPC alloy. However, a portion of NPC alloy may be formed that issubstantially free of reinforcing agent (i.e., non-reinforced NPCalloy). Typically, a contiguous portion of non-reinforced NPC alloy isintegrally connected with the reinforced NPC alloy and is formed on oneside of the composite, usually its topside. To the extent the compositeis made with a contiguous portion of non-reinforced NPC alloy layer, thenon-reinforced contiguous portion is preferably less than about 2.5 mmdeep. More preferably, the non-reinforced contiguous portion is lessthan about 1 mm deep and most preferably, it is less than 0.5 mm deep.

Also, the portions of non-reinforced NPC alloy formed may also benon-contiguous. In that case, however, the percentage of non-contiguousnon-reinforced portions should be limited so that the overall structuralintegrity needed for composite's specific application is notcompromised.

When the reinforcing agent comprises a substrate having a porousstructure, the MCX mixture is added to the porous substrate so that anintimate distribution of the mixture in and/or on the substrate isachieved. When the MCX mixture is polymerized, a layer of NPC alloy maybe formed on top of the substrate. But, because the MCX mixture isintimately distributed in and/or on the substrate, the layer on top ofthe substrate is also an integral part of the NPC alloy in the substrateand, therefore, an integral part of the composite.

When the reinforcing agent comprises non-aggregated fibers, thereinforcing agent is mixed into the MCX mixture. The MCX/fiber mixtureis then distributed into a mold prior to polymerization. Alternatively,non-aggregated fibers may be distributed in a mold and the MCX mixtureis poured over the fibers. The mold may be such so as to produce asheet-like material or another suitable shape for other applications.The MCX/fiber mixture may be distributed in a mold, for example, withoutlimitation, vibration, hydraulic loading, pressure, and combinationsthereof.

The MCX mixture may be intimately distributed in and on the poroussubstrate by, for example, without limitation, vibration, rolling,scrubbing, spraying, hydraulic loading, pressure, vacuum andcombinations thereof.

It will be understood that if a pre-formed geosynthetic dual liner isused or if the geomembrane is fused prior to polymerization, thatintimate distribution means, other than a vacuum, will be used tointimately distribute the MCX mixture in and on the porous substrate.

Polymerization

After the MCX mixture is intimately distributed in, on and/or among thereinforcing agent, the polymerization process begins while thecross-linking agent, acting in concert with the polymerization process,helps to form a networked polymer/clay alloy structure that isintimately integrated with the reinforcing agent. Polymerization of theMCX mixture is initiated by a polymerization initiator means forgenerating an ionic or free radical monomeric species. Initiation may beaccomplished by adding a suitable chemical substance to the MCX mixture.Also, electromagnetic radiation having a wavelength of 10 nanometers(nm) or less may be used alone or in combination with a chemicalinitiator.

Suitable chemical substances for initiating polymerization include,without limitation, free radical initiators, carbanions, carbonium ions,and combinations thereof.

Examples of free radical initiators include, without limitation, thermalinitiators, and redox systems, which are typically two or morechemicals, which are added simultaneously as different solutions.

Examples of thermal initiators include, without limitation, (1) alkalimetal salts of sulfite, bisulfite, persulfate, benzoyl peroxide, andcombinations thereof, (2) ammonium salts of sulfite, bisulfite,persulfate, benzoyl peroxide, and combinations thereof, (3)2,2′-azobis(2-amidino-propane)-dihydrochloride, (4)2,2′-azobis(4-cyanopentanoic acid), and combinations thereof.

The desired polymerization temperature for forming an NPC alloycomposite is primarily dependent on the type and concentration ofinitiator means selected. For example, lower polymerization temperaturesmay be used where a thermal initiator prone to forming free radicals ata lower temperature (e.g., about 40° C. to about 50° C.) is used. Thus,where the polymerization reaction used for making the NPC alloy isinitiated with a thermal initiator, the reaction is preferably at atemperature in a range of from about 40° C. to about 95° C. Morepreferably, however, the reaction temperature is at a temperature in arange of from about 60° C. to about 85° C. and most preferably, in arange of from about 65° C. to about 80° C. Also, where a high energyradiation source, such as gamma ray radiation is used, thepolymerization reaction may be conducted as low as about ambienttemperature, for example about 20° C.

The polymerization reaction time is also primarily dependent on the typeof initiator means used and its concentration. However, other factorsaffecting the desired reaction time include the type of monomer and itsconcentration, the depth of the MCX mixture and the amount ofreinforcing agent (e.g., MCX mixture thickness as applied on thesubstrate or volume of non-aggregated fibers in the MCX mixture). Also,once a polymerization reaction is initiated, typically, it will notterminate in response to a sharp temperature drop. For example, once theMCX mixture is exposed to the desired initiation temperature, thepolymerization reaction will proceed for some time thereafter, dependingon the reaction temperature selected, the time period that the MCXmixture is exposed to the selected temperature (i.e., heat exposureperiod) and the composite's heat retention. Also, we have discoveredthat higher initiator concentrations generally produce residual monomerconcentrations of about 200 ppm or less. However, these higher initiatorconcentrations are more likely to promote premature polymerizationunless the temperature is kept sufficiently below 40° C. Accordingly, itis important to maintain the MCX mixture below 40° C. before the mixtureis distributed in, on and/or among the reinforcing agent so that themixture's viscosity is sufficiently low to ensure the mixture isintimately distributed in, on and/or among the reinforcing agent.

The time period that the MCX mixture is exposed to the selected reactiontemperature may be in a range from as low as about 1 minute to as highas about 24 hours. For example, where an MCX mixture having a clay tomonomer ratio of about 2:1 is pressed into a porous substrate to a depthof about 2-3 mm, potassium persulfate is used as a thermal initiator andthe selected temperature is about 80° C., the duration of the heatexposure period is preferably in a range of from about 2 minutes toabout 60 minutes. More preferably, under similar conditions, the heatexposure period is in a range of from about 2 minutes to 45 minutes and,most preferably, in a range from about 3 minutes to about 30 minutes.

Examples of redox systems include, without limitation,persulfate/bisulfite, persulfate/thiosulfate, persulfate/ascorbate,hydrogen peroxide/ascorbate couples, and combinations thereof.Typically, additional heat is not required when using a redox systemsinitiator because the reactions are often exothermic, so such systemscan work effectively at temperatures in a range of from about thefreezing point of the MCX mixture to the boiling point of the mixingfluid. Typically, the temperature is ambient, about 20° C.

Alternatively, polymerization may be initiated by electromagneticradiation having a wavelength below about 10 nm such as, for example,without limitation, by gamma rays, X-rays, or high energy sub-atomicparticles. In such a case, the polymerization reaction is typicallyconducted at ambient temperatures. However, the temperature can behigher or lower.

However, it is well known to those skilled in the art that UV radiation,with wavelengths ranging from about 200 nm to 390 nm is not suitable forpolymerization initiation of the MCX mixture because the clay willinterfere with UV light's ability to penetrate into the sample, andthereby initiate the polymerization reaction, even with aphoto-initiator present. More specifically, it is believed that the claypreferentially absorbs the UV light, thereby inhibiting the UV light'seffectiveness as an initiator means.

Optionally, once polymerized, all or a portion of the mixing fluidremaining in the reinforced NPC alloy composite product may be removed,for example by desiccating at room temperature or oven-drying. Ifoven-dried, the composite should be dried at a temperature that does notadversely affect the properties or characteristics of the product, forexample, at a temperature less than about 110° C.

The moisture content of the reinforced NPC alloy composite product isdependent on the application and other factors. For example, a highermoisture content composite provides greater flexibility and a lowerinitial permeability. But a lower moisture content composite can havereduced transportation costs. Consequently, the desired moisture contentwill be determined by the environment in which the composite productwill be used and maximum acceptable transportation costs.

Therefore, for a composite product with at least some flexibility, themoisture content is preferably in a range of from about 25% to about 75%by weight.

Reinforced NPC Alloy Composite

In use, the NPC alloy swells on contact with water as the alloy absorbswater. The expanded NPC alloy swells in and/or around the reinforcingagent. It is believed that the alloy swells and expands into anyinterstitial spaces that were not occupied by the NPC alloy when thecomposite was formed. Also, it is believed that the alloy expands aroundthe reinforcing agent itself. Consequently, the composite swellssubstantially as an integrated unit while only negligible amounts ofclay, if any (i.e., substantially no clay), separate from the compositewhen it is immersed in water at a temperature in a range of from about1° C. to about 60° C., whether the water is saline or not.

It will be understood by those skilled in the art that the degree towhich the NPC alloy is networked will affect the alloy's capacity toabsorb water. Of course, if insufficient cross-linking agent is used,the NPC alloy may become water soluble under certain conditions and theclay could then substantially separate from the alloy. On the otherhand, if excessive amounts of cross-linking agent are used, the NPCalloy may be so inflexible that it is unable to absorb sufficientamounts water and thereby reach either the desired fluid permeabilityand/or water absorption performance.

In containment applications, the reinforced NPC alloy composite productis often under a confining stress due to overburden. Under a standardeffective confining stress of 20 kPa or 2.9 psi, the flux (i.e., therate water travels at the specified pressure) of the composite is about10⁻⁸ m³/m²/s or less, as measured by ASTM 5887-95. As the confiningstress increases with additional overburden, the hydraulic conductivityof the composite will decrease because the composite will becomecompressed.

Cover Sheet

A cover sheet is advantageously used to (1) assist in MCX mixturedistribution, for example, when using a vacuum, (2) reduce evaporationand/or boiling of mixing fluid or other components in the MCX mixtureduring polymerization, and/or (3) assist in handling, for examplerolling, and storage of the composite.

In one embodiment, a cover sheet can be contacted with the MCX mixtureeither during or shortly after the mixture is contacted with thereinforcing agent. Moreover, the cover sheet may be applied to one orboth sides of the reinforcing agent contacted with the MCX mixture. Butpreferably, the cover sheet is applied to one side, and more preferably,the cover sheet is applied to the side opposing the side on which themeans for distributing the MCX mixture (e.g., vacuum, roller, pressure,etc.) is applied. Most preferably, the cover sheet is concurrentlycontacted with the MCX mixture and reinforcing agent, while a vacuum isapplied to the opposing side and thus the mixture is intimatelydistributed in, on and/or among the reinforcing agent.

In another embodiment, the cover sheet may be applied to one or bothside of the reinforced NPC alloy composite after polymerization. Ifdesired, the cover sheet may be self-adhering to the composite or may beadhered to the composite, for example, without limitation, by heatbonding or an adhesive.

Examples of suitable cover sheets include, without limitation,polyethylene film, sulfite and sulfate papers, kraft papers, groundwoodpapers, filter papers, woven and non-woven natural and syntheticfabrics, fiberglass, and combinations thereof. The cover sheet may beremoved after polymerization or left in place, depending on thecomposite's ultimate application.

Illustrative Process

FIGS. 1-3 illustrate a process for producing a reinforced NPC alloycomposite 10. A reinforcing agent, in this case a porous substrate 12,is fed onto a conveyor 26, using feeder rollers 28, 30.

An MCX mixture 14 is prepared in vessel 16, by mixing at least amonomer, clay particles, a cross-linking agent and a mixing fluid untilthe mixture is substantially homogeneous. Preferably, the MCX mixture 14is maintained in the vessel 16 at a temperature less than about 40° C.,to reduce premature polymerization of the monomer.

The MCX mixture 14 is metered from the vessel 16 and contacts the poroussubstrate 12 as it moves along the conveyor 26. A cover sheet 24 isplaced on top of the MCX mixture 14 using a guiding roller 36.

In the embodiment illustrated in FIG. 1, the porous substrate 12 iscontacted with the MCX mixture 14, using a roller 18, until the mixture14 is distributed in and on the substrate 12.

In the embodiment illustrated in FIG. 2, the porous substrate 12 iscontacted with the MCX mixture 14, using a piston 20, until the mixture14 is intimately distributed in and on the substrate 12. Piston 20 maybe a mechanical or gas piston.

In the embodiment illustrated in FIG. 3, the porous substrate 12 iscontacted with the MCX mixture 14, using a vacuum means 32, until themixture 14 is intimately distributed in and on the substrate 12.

In all the illustrated embodiments, after the MCX mixture 14 isintimately distributed in and/or on the porous substrate 12, the mixture14 is, in accordance with the above discussion, polymerized within andon the substrate 12 by heating the combined substrate 12 and mixture 14in a heating zone 22 to form the reinforced NPC alloy composite 10. Thereinforced NPC alloy composite 10 can be rolled and packaged forsubsequent handling and transport, if desired.

The following non-limiting examples of embodiments of the presentinvention that may be made and used as claimed herein are provided forillustrative purposes only.

EXAMPLE 1 Effect of Clay to Monomer Ratio on Water Absorption Capacity

NPC Alloy Preparation

Seven MCX mixtures were prepared in the amounts shown in Table 1. Clayto monomer weight ratios ranged from 0.1 to 9.62 in the seven MCXmixtures. The clay used in the MCX mixtures was NATURAL GEL™, a naturalswelling clay often referred to as Wyoming bentonite, commerciallyavailable from American Colloid. The monomer was acrylamide, obtainedfrom Cytec, West Paterson, N.J. A Control sample was made usingacrylamide monomer without added clay.

Water, sodium hydroxide (NaOH), sodium bicarbonate (NaHCO₃), EDTA,acrylamide, N,N′-methylene bisacrylamide (NBAM) and potassium persulfate(K₂S₂O₈) were mixed in a 250-mL HDPE bottle. The aqueous solution wasmixed well, prior to addition of clay. Clay was added and mixed again toform a homogeneous MCX mixture. All MCX mixtures were viscous but fluidbefore polymerization.

TABLE 1 Sample (g) Component Control 1 2 3 4 5 6 7 Water 79.98 72.598.778 74.4 291.153 74.4 151.23 91.91 NaOH 3.768 3.108 3.904 2.28 7.4981.891 1.563 0.506 NaHCO₃ 0.931 0.802 0.931 0.60 0.204 0.468 0.323 0.105EDTA 0.109 0.09 0.116 0.08 0.217 0.06 0.042 0.025 Acrylamide 25.07321.028 24.871 15.00 50.00 7.72 10.042 2.294 NBAM 0.057 0.05 0.058 0.040.123 0.028 0.022 0.012 K₂S₂O₈ 0.21 0.183 0.217 0.132 0.418 0.085 0.0880.032 Clay — 2.121 8.368 7.502 50.22 15.389 30.00 22.029 Total (g)110.128 99.882 137.243 100.034 399.833 100.041 193.31 116.913Clay:Monomer 0 0.10 0.34 0.50 1.00 2.00 3.00 9.60 Ratio (wt)

The Control and MCX mixtures were left in an oven overnight at 65° C.for polymerization. After polymerization, the Control and NPC alloyswere transferred to glass dishes and dried at 105° C. for 48 hours.

Water Absorption Capacity (WAC) of NPC Alloys

Approximately 1 gm of each NPC alloy and the Control was placed in a 500mL HDPE bottle with 400 ml distilled water. After 48 hours, free waterwas decanted off the swollen NPC alloy using a 115 mesh screen.

The swollen NPC alloy was weighed and the water absorption capacity(WAC) was calculated according to the following equation:${WAC} = \frac{\left( {{H_{2}O\quad {Swollen}\quad {NPC}{\quad \quad}{Alloy}\quad {Mass}} - {{Dried}\quad {NPC}\quad {Alloy}\quad {Mass}}} \right)}{{Dried}\quad {NPC}\quad {Alloy}\quad {Mass}}$

A projected WAC, WAC_(prj), based on the Control WAC and clay contentwas also calculated according to the following equation:${WAC}_{prj} = {\left( {\frac{{Parts}\quad {Monomer}}{{{Total}\quad {Parts}\quad {Monomer}} + {Clay}} \times \begin{matrix}{Control} \\{WAC}\end{matrix}} \right) + \left( {\frac{{Parts}\quad {Clay}}{{{Total}\quad {Parts}\quad {Monomer}} + {Clay}} \times \begin{matrix}{{Max}.\quad {Est}.} \\{{Clay}\quad {WAC}}\end{matrix}} \right)}$

where the Control WAC=352 and the Maximum Estimated WAC for clay=10. Forexample, where a 1:3 clay to monomer ratio is used to produce the NPCalloy, the NPC alloy's WAC_(prj) is [(¾)×352]+(¼)10=266. Likewise, wherea 2:1 clay to monomer ratio is used, the NPC alloy's WAC_(prj) is[(⅓)×352]+(⅔)10=124.

Finally, the monomer WAC (WAC_(m)) was also calculated to determine thewater absorption capacity based on the amount of monomer used to producethe polymer/clay alloy sample being tested. The WAC_(m) was calculatedaccording to the following equation:${WAC}_{m} = \frac{\left( {{H_{2}O\quad {Swollen}\quad {NPC}{\quad \quad}{Alloy}\quad {Mass}} - {{Dried}\quad {NPC}\quad {Alloy}\quad {Mass}}} \right)}{\quad {{Mass}\quad {of}\quad {Monomer}\quad {used}\quad {to}\quad {produce}\quad {NPC}\quad {Alloy}}\quad}$

The results are tabulated in Table 2.

TABLE 2 Sample ID Control 1 2 3 4 5 6 7 Clay:Monomer Ratio 0.00 0.100.34 0.50 1.00 2.00 3.00 9.61 WAC g H₂O per g 352 339 332 213 207 134 8314 WAC_(prj) NPC alloy 321 266 238 181 124 96 42 WAC_(m) g H₂O per g 421441 472 364 414 403 349 250 monomer in NPC alloy

As shown in Table 2, the WAC for NPC alloy Samples 1 and 2 is 339 and332, respectively. This means that the NPC alloy absorbs 339 and 332times its own weight in water for these two samples, respectively,versus a 352 WAC for the clay-free Control. Bentonite clay typically hasa paste-like consistency up to a water absorption of 5 to 10 times itsweight, after which the clay becomes dispersed in water to form aslurry. Consequently, because bentonite clay is not known as beinghighly water-absorbent on a per unit mass basis, as compared with awater-absorbent polymer, the drop in WAC shown in Table 2 withincreasing clay to monomer ratio was a surprising and unexpected result.

For example, at a 1:1 ratio, those skilled in the art might haveprojected a WAC of just slightly more than 0.5× the Control's WACbecause only half of the NPC alloy is networked polymer. So, taking intoaccount the water absorption for clay alone (i.e., about 5-10), a 1:1clay to monomer ratio in an NPC alloy would have been expected to be, atbest, about ½ the Control's WAC (i.e., 176) plus 5 for the clay'sexpected water absorption for a WAC_(prj) of 181. But Sample 4, with a1:1 clay to monomer ratio, has a 207 WAC, which is 14.4% greater thanexpected. Similarly, a 2:1 clay to monomer ratio has a WAC_(prj) ofabout 124, while Sample 5 produced a 134 WAC, which is 8.1% greater thanexpected. The general trend is that WAC, across a broad range of clay tomonomer ratios, is substantially comparable, if not slightly improvedversus the clay-free Control until a significantly high clay loading inthe NPC alloy is reached. At a significantly high clay loading, itappears that the polymer loading is so low that the clay's inherent WACis dominant.

This is a surprising and unexpected result, particularly at high clay tomonomer ratios of 2:1 and 3:1. Ogawa et al (“Preparation ofMontmorillonite-Polyacrylamide Intercalation Compounds and the WaterAbsorbing Property” Clay Science 7:243-251; 1989) suggest on pg. 250that clay acts as a cross-linking agent. Thus, Ogawa et al suggest thatclay would act in concert with a cross-linking agent in an MCX mixtureto severely constrain a polymer formed from that mixture. Moreover, theresults in Example 2 illustrate that a cross-linking agent concentrationas low as about 0.1 wt. % can over cross-link a polymer, therebysubstantially reducing its water absorption capacity. Thus, thesensitivity of WAC to excess cross-linking agent and Ogawa et al suggestthat increasing the clay content would produce a highly constrained NPCalloy with inhibited WAC. Consequently, it is surprising and unexpectedthat using an MCX mixture with both a cross-linking agent and clay, forexample, at a 2:1 clay to monomer ratio, would produce an NPC alloy withcomparable or slightly better performance than the clay-free Control.

When calculated on the basis of an equivalent amount of acrylamidemonomer used to produce an alloy, the WAC_(m) of the polymer/clay alloysSamples 1-5 is similar to that of the Control sample. As mentionedabove, monomers are more costly than clay. Thus, the WAC_(m) resultsdemonstrate the economic advantages of the NPC alloy.

Table 2 demonstrates that good WAC results were obtained for thecomposition described in Table 1 in a clay to monomer ratio of about 0.3to about 3.0. The optimal clay to monomer ratio will depend on theintended use of the compositions falling within the scope of the claimedinvention. For instance, beyond adjusting the clay to monomer ratio, asdiscussed more fully under Example 2, the cross-linking agent to monomerratio can also be adjusted to increase or decrease the WAC to thedesired level.

For example, as a landfill liner, a WAC for the reinforced NPC alloycomposite only needs to be high enough to ensure that the NPC alloyswells sufficiently to occupy any interstitial spaces that were notoccupied by NPC alloy when the composite was formed. This degree ofswelling will ensure that the composite has sufficiently lowpermeability to water and other fluids. For example, the WAC for an NPCalloy used in a landfill liner composite could be as low as about 5. Ofcourse, a higher WAC up to about 500 could also be used in a landfillliner composite. However, a WAC significantly much higher than 50 couldreduce the structural integrity of the composite due to excess water.

Consequently, in personal care type applications, where the composite'sstructural integrity is likely to be a factor as well, a WAC in a rangeof from about 20 to about 100 would be most likely desired for thecomposite.

Accordingly, the above data illustrates that the unique polymer/clayalloy can provide effective water absorption for a reinforced NPC alloycomposite. As well, the clay component in the NPC alloy provides a costeffective means to make a reinforced NPC alloy composite whiledelivering the water absorbing and/or permeability property performancedesired for the intended use.

EXAMPLE 2 Effect of Cross-Linking Agent to Monomer Ratio on WAC

NPC Alloy Preparation

Three MCX mixtures were mixed in the amounts shown in Table 3. Thecross-linking agent to monomer weight ratios ranged from 1.10×10⁻³ to9.41×10⁻³ in the three MCX mixtures. The clay to monomer weight ratiowas held constant at about 1:1. The clay used in the MCX mixtures wasNATURAL GEL™. The monomer was a 1:4 (wt) mixture of acrylic acid(Aldrich) and acrylamide (Cytec).

Water, NaOH, sodium carbonate (Na₂CO₃), acrylic acid, acrylamide, NBAMand K₂S₂O₈ were mixed in the proportions shown in Table 3 in a 2-LErlenmeyer flask. The aqueous solution was mixed well, prior to additionof clay. Clay was added and mixed again to form a homogeneous MCXmixture. All MCX mixtures were viscous but fluid before polymerization.

TABLE 3 Sample (g) Component 8 9 10 Water 1000 1000 1000 NaOH 10 10 10Na₂CO₃ 12 12 12 Acrylic Acid (AA) 20 20 20 Acrylamide (AM) 80 80 80 NBAM0.941 0.303 0.11 K₂S₂O₈ 0.6 0.6 0.6 Clay 99 105 105 Total (g) 1222.5411227.903 1227.71 NBAM/(AA + AM) 9.41 3.03 1.10 Wt Ratio (× 10³)

The MCX mixtures were left in an oven overnight at 65° C. forpolymerization. After polymerization, the NPC alloys were transferred toglass dishes and dried at 105° C. for 48 hours.

Water Absorption Capacity (WAC) of Polymer/Clay Alloys

Approximately 1 gm of NPC alloy Sample 8 was placed in a 500 mL HDPEbottle with 400 ml distilled water. After 48 hours, free water wasdecanted off the swollen NPC alloy using a 115 mesh screen.

The swollen NPC alloy was weighed and the water absorption capacity(WAC) was calculated as described in Example 1. Samples 9 and 10 weretreated in the same manner. The results are tabulated in Table 4.

The monomer WAC (WAC_(m)) was also calculated to determine the waterabsorption capacity based on the amount of monomer used to produce theNPC alloy sample being tested. These results are also tabulated in Table4.

TABLE 4 Sample 8 9 10 NBAM/(AA + AM) Wt 9.41 3.03 1.10 Ratio (× 10³) WACg H₂O per g 145 281 281 polymer/clay alloy WAC_(m) g H₂O per g 324 641640 monomer in polymer/clay alloy

As shown in Table 4, the NPC alloy's WAC increases as the cross-linkingagent to monomer ratio decreases from 9.41×10⁻³ to 3.03×10⁻³. However,it is believed that a further significant decrease in cross-linkingagent to monomer ratio (e.g., to about 0.10×10⁻³) would sufficientlyreduce the mechanical strength of the NPC alloy's networked polymer andthereby limit NPC alloy's ability to absorb and retain water.

Of course, to the extent the polymer is not cross-linked, the polymerwill dissolve in water. Also, at low levels of cross-linking, thepolymer may fracture and become water-soluble. However, if the degree ofcross-linking is too high, there is too much constraint on the polymerand its water absorption capacity is reduced.

Accordingly, the above data illustrates that the unique NPC alloy canprovide effective water absorption for a reinforced NPC alloy composite.As well, controlling the cross-linking agent to monomer ratio, alone orin combination with the clay to monomer ratio, provides a means fordesigning the water absorbing and/or permeability property performancedesired for the composite's intended use.

EXAMPLE 3 Hydraulic Conductivity of Reinforced Networked Polymer ClayAlloy Composite

Monomer/Clay Mixture Preparation

Two MCX mixtures were prepared in the amounts shown in Table 5. The clayto monomer weight ratios were 1:1 and 2:1 in Samples 11 and 12,respectively. The clay used in the MCX mixtures was NATURAL GEL™. Themonomer was acrylamide.

Water, NaOH, NaHCO₃, EDTA, acrylamide, NBAM and K₂S₂O₈ were mixed in theproportions shown in Table 5 in a 2-L Erlenmeyer flask. The aqueoussolution was mixed well, prior to addition of clay. Clay was added andmixed again to form a homogeneous MCX mixture. The MCX mixtures wereviscous but fluid before being contacted with the reinforcing agent.

TABLE 5 11 12 Component (g) (g) Water 291.153 74.4 NaOH 7.498 1.891NaHCO₃ 0.204 0.468 EDTA 0.217 0.06 Acrylamide 50.00 7.72 NBAM 0.1230.028 K₂S₂O₈ 0.418 0.085 Clay 50.22 15.389 Total (g) 399.833 100.041Clay to Monomer Ratio 1.00 1.99 (wt)

Reinforced NPC Alloy Composite Preparation

PETROMAT™ 4597 and AMOCO 4551™ (Amoco) geotextiles were used asreinforcing agent. These commercially available geotextiles are nonwovenfabrics comprising polypropylene fibers. The unit weight for PETROMAT™4597 and AMOCO 4551™ is 0.14 kg/m² and 0.2 kg/m², respectively. Thegeotextiles were about 1-3 mm thick. The thickness typically varies in anon-woven geotextile and it is difficult to measure because of thefibers.

Reinforced Sample A1 was prepared by pouring Sample 11 MCX mixture in athickness of about 2.5 mm thickness onto a 20 cm×20 cm piece ofPETROMAT™ 4597 geotextile, representing a loading of about 2.5 kg/m².The MCX mixture was intimately distributed in and on the geotextilematerial using a wooden rolling pin.

Reinforced Sample A2 was prepared in the same manner as Sample A1 usingSample 12 MCX mixture and AMOCO 4551™ geotextile.

Reinforced Sample A3 was prepared using Sample 11 MCX mixture and twolayers of AMOCO 4551™ geotextile. The MCX mixture was poured onto onelayer of geotextile (i.e., bottom layer) and then covered with thesecond layer of geotextile (i.e., top layer). The MCX mixture wasintimately distributed in and on both layers using a wooden rolling pin,though the mixture was primarily substantially embedded throughout thebottom layer.

The reinforced MCX mixture samples was placed between two glass platesand put into an oven at 75° C. for 2 hours for polymerization. Spacerswere placed between the glass plates so that the polymerized sampleswould be of substantially uniform thickness, without added pressureduring polymerization. The glass plates also reduced evaporation of MCXmixture components during polymerization.

Reinforced Samples A1 and A2 were dried in an oven at 80° C. overnight.Sample A3 was not dried, but was stored in a polyethylene bag directlyafter polymerization. Though Samples A1 and A2 were dried, it ispreferable to use the reinforced NPC alloy composite in an non-driedstate, as in Sample A3.

Hydraulic Conductivity Test

The rate of water flow through a layer of the reinforced NPC alloycomposite samples under a hydraulic gradient was measured using ASTM5887-95.

ASTM 5887-95 is a standard method to measure the flux or flow of waterper unit area through the sample. The test specimen was set up in aflexible wall permeameter, subjected to a total stress of 550 kPa and aback pressure of 515 kPa for a period of 48 hours. Flow of deionizedwater was initiated by raising the pressure on the influent side of thetest specimen to 530 kPa. This places an effective confining stress onthe specimen of approximately 20 kPa. All samples were tested at 20 kPa,except Sample A2, which was tested at 120 kPa. The flux was determinedwhen inflow and outflow were approximately equal.

Because the sample's thickness has an influence on its hydraulicconductivity, the flux determined by the ASTM 5887-95 test was used tocalculate hydraulic conductivity based on each sample's differentthickness. The hydraulic conductivity results in Table 7 were calculatedas follows:

k/μ=(Q/A)(ΔL/Δp)

K=ρg(k/μ)

where k is permeability, μ is fluid viscosity, (Q/A) is flux, (ΔL/Δp) isthe reciprocal of the pressure gradient, which accounts for variationsin the sample's thickness and thereby normalizes k/μ and hence K, K ishydraulic conductivity, ρ is fluid density and g is a gravitationalconstant.

In addition, the change in specimen thickness was measured and used tocalculate the percentage of swelling during the test.

The results of the hydraulic conductivity tests are tabulated in Table7. BENTOMAT® ST (CETCO, Arlington, Ill.) was used as a comparativesample. BENTOMAT® ST is a GCL consisting of a sodium bentonite layer(approximately 4.9 kg/m²) between woven and non-woven geotextiles, whichare needle-punched together.

The initial and final thicknesses are shown in Table 7 as T₀ and T_(f),respectively. The unit weight shown in Table 7 for Samples A1 and A2 ison a moisture-free basis. Sample A3 was not dried after polymerizationand, therefore, the exact loading on a moisture-free basis is not known.However, it is estimated that the unit weight on a moisture-free basisis less than 0.75 kg/m².

For convenience, the MCX mixture and geotextile used in each sample issummarized in Table 6.

TABLE 6 Reinforcing Monomer/Clay Sample Agent Mixture A1 PETROMAT 114597 A2 AMOCO 4551 12 A3 Double AMOCO 11 4551 Comparative BENTOMAT STN/A

TABLE 7 Sam- Weight T₀ T_(f) Swell σ_(effective) Flux ple (kg/m²) (mm)(mm) (%) (kPa) (m³/m²/s) K (cm/s) A1 0.64 1.08 4.80 344 20 4.8 × 10⁻⁹1.5 × 10⁻⁹  A2 0.96 1.70 2.19 29 120 3.7 × 10⁻⁹ 5.1 × 10⁻¹⁰ A3 <0.753.89 6.92 78 20 1.6 × 10⁻⁹ 7.2 × 10⁻¹⁰ Com- 4.90 6.20 8.68 40 20 3.2 ×10⁻⁹ 2.0 × 10⁻⁹  para- tive

The water flux through Samples A1 and A3 was similar to the flux throughthe comparative sample at an effective confining stress of 20 kPa. Evenat this very low NPC alloy loading (as little as 0.64 kg/m², where theweight of the NPC alloy is calculated on a water-free basis), thereinforced composite is as effective as GCL with 4.9 kg/m² bentonite.The average hydraulic conductivity (K) for Samples A1 and A3 of 1.1×10⁻⁹cm/s, which is about a 50% improvement versus the comparative sample's Kof 2.0×10⁻⁹ cm/s. This improved K value is particularly significantsince hydraulic conductivity tends to increase as the confining stressapproaches zero, as discussed more fully in Example 5. However, thisdata demonstrates the composite's surprising and unexpected ability todeliver relatively consistent hydraulic conductivity performance underboth lower confining stress and higher confining stress conditions.

The flux through Sample A2 was tested at a confining stress of 120 kPato determine the effect of the confining stress on flux andcorresponding hydraulic conductivity. The flux through Sample A2 wassimilar to the flux through Samples A1 and A3 and the hydraulicconductivity was similar to Sample A3. Accordingly, there was littlechange when the confining stress was increased from 20 kPa to 120 kPa.

Accordingly, the reinforced NPC alloy composite provides a hydraulicconductivity performance at least comparable to, if not better than,conventional GCL, but weighing substantially less than GCL and having adramatically improved clay retention capacity versus GCL when exposed towater. In turn, this contributes significantly to the composite'slong-term hydraulic conductivity performance, which will remainrelatively stable over long-term and persistent water exposure in theenvironment. Meanwhile, under similar environmental conditions, thehydraulic conductivity for GCL will deteriorate over time as clayparticles migrate through the GCL fabric layer as discussed more fullyunder Example 8.

EXAMPLE 4 One Alternative Preparation of Reinforced Networked PolymerClay Alloy Composite

Reinforced NPC Alloy Composite Preparation

Reinforced Samples B1 and B2 were prepared in the same manner asReinforced Sample A3 in Example 3 using Sample 11 MCX mixture (seeExample 3) and 2 layers of AMOCO 4551™ geotextile. The geotextilematerial was intimately contacted with the MCX mixture using a TEFLON™coated piston, with pressure applied by hand, until the mixture wassubstantially distributed throughout the material. It appeared that theMCX mixture was more evenly distributed using the piston, as comparedwith the wooden rolling pin used in Example 3.

The reinforced MCX mixture samples was placed in an oven at 65° C. for 2hours for polymerization.

The reinforced samples were stored in a polyethylene bag directly afterpolymerization.

Hydraulic Conductivity Test

The test procedures for hydraulic conductivity measurement were the sameas those in Example 3. The results are tabulated in Table 8 with theresults for the same comparative sample used in Example 3.

TABLE 8 Weight T₀ Swell σ_(effective) Flux Sample (kg/m²) (mm) (%) (kPa)(m³/m²/s) K (cm/s) B1 <0.75 3.61 112 20 2.7 × 10⁻⁹ 1.4 × 10⁻⁹ B2 <0.753.67 114 20 3.0 × 10⁻⁹ 1.6 × 10⁻⁹ Comparative 4.90 6.20 40 20 3.2 × 10⁻⁹2.0 × 10⁻⁹

The water flux and K through samples B1 and B2 was similar to the fluxand K through the comparative sample at an effective confining stress of20 kPa. Even at this very low NPC alloy loading (<0.75 kg/m², where theweight of the NPC alloy is calculated on a water-free basis), thereinforced composite is as effective as GCL with 4.9 kg/m² bentonite(dry weight).

Accordingly, the reinforced NPC alloy composite provides a hydraulicconductivity performance at least comparable to, if not better than,conventional GCL, but weighing substantially less than GCL and having adramatically improved clay retention capacity versus GCL when exposed towater. In turn, this contributes significantly to the composite'slong-term hydraulic conductivity performance, which will remainrelatively stable over long-term and persistent water exposure in theenvironment. Meanwhile, under similar environmental conditions, thehydraulic conductivity for GCL will deteriorate over time as clayparticles migrate through the GCL fabric layer as discussed more fullyunder Example 8.

EXAMPLE 5 Flux at Zero Confining Stress

Sample Preparation

Samples were prepared using the following MCX mixture having a clay tomonomer ratio of 2:1:

100.8 g (1.52 wt. %) acrylic acid

400.5 g (6.04 wt. %) acrylamide

55.1 g (0.83 wt. %) NaOH

51.5 g (0.78 wt. %) Na₂CO₃

1.62 g (0.02 wt. %) NBAM

12.8 g (0.19 wt. %) potassium persulfate

1000.8 g (15.09 wt. %) clay

5009.9 g (75.53 wt. %) water

Reinforced NPC alloy composites were prepared using the MCX mixture andTERRAFIX® 270R-A geotextile.

Samples were prepared in a semi-continuous process, as discussed aboveand illustrated in FIG. 3, to distribute the MCX mixture in thegeotextile and form the composite. The MCX mixture was applied to thegeotextile as described below for each set of samples. A polyethylenefilm cover sheet was placed on top of the MCX mixture and a vacuum wasapplied to the sample from the geotextile's opposing side. The MCXmixture was intimately distributed in and on the geotextile material byapplying the vacuum. The cover sheet reduced channeling through thesample and the MCX mixture was more evenly distributed through thegeotextile, as compared with a sample prepared without a cover sheet.

For Samples 13 and 14, the MCX mixture was poured in a thickness ofabout 3.5 mm onto a 0.95 m×0.97 m piece of geotextile. A second layer ofthe geotextile was placed on top of the MCX mixture. A polyethylene filmcover sheet was placed on top of the second geotextile layer and avacuum pressure of about 20 kPa was applied to the opposing side of thefirst geotextile layer.

For Samples 15 and 16, the MCX mixture was poured in a thickness ofabout 2.5 mm onto a 0.95 m×0.50 m piece of geotextile. A polyethylenefilm cover sheet was placed on top of the MCX mixture and a vacuumpressure of about 16 kPa was applied to the geotextile's opposing side.

Samples 17 and 18 were prepared substantially the same as Samples 15 and16, but using a vacuum pressure of about 15 kPa, instead of 16 kPa.

All samples were heated in the semi-continuous process using aCATA-DYNE™ infrared heater (placed about 500 mm above the sample) at atemperature of about 80° C. for 10 minutes to form the reinforced NPCalloy composite.

Samples were cut into 9.0 cm discs using a high speed drill cutter andweighed. The results are presented in Table 9.

TABLE 9 Unit Weight Sample (kg/m²) 13 3.47 14 2.92 15 2.73 16 2.90 172.42 18 2.46

Hydraulic Conductivity Tests

The hydraulic conductivity tests used to evaluate Samples 13-18 werebased on a modified ASTM 5887-95 test. The apparatus used for the testwas a Baroid filter press. Compressed air was used to apply pressurethrough a pressure manifold. Unlike ASTM 5887-95, under this hydraulicconductivity test, no confining stress was applied to the sample. Asmentioned previously, the hydraulic conductivity of a liner willgenerally decrease with increased confining stress. Accordingly, thehydraulic conductivities illustrated in this example, with zeroconfining stress applied, represents a “worst case scenario” where theliner may, at least early in its life, be exposed to confining stressesthat are low or near zero.

The samples were placed at the bottom of the filter apparatus followedby a rubber gasket, cell and cap. The assembly was inserted into thesupport stand, sealed by tightening a “T” screw and then connected tothe pressure manifold. The test fluid was then introduced to the celland the sample was pre-soaked in the test fluid for 2 hours atatmospheric pressure.

After 2 hours, a flow pressure of 15 kPa was applied. Effluent wasweighed, at an interval of minutes at the beginning of test and severalhours thereafter.

The amount of effluent was used to calculate the flux through thesample, using an effective flow area of 7.7 cm diameter.

In this example, deionized water was used as the test fluid.

The water flux through the samples was measured at 48 hours. These waterflux results are presented in Table 10.

TABLE 10 Projected Hydraulic Conductivity Water Flux @ 48 hours Based onSample (m³/m²/s) 2 mm Thickness 6 mm Thickness 13 4.87 × 10⁻⁹ 6.36 ×10⁻¹⁰ 1.91 × 10⁻⁹ 14 6.44 × 10⁻⁹ 8.41 × 10⁻¹⁰ 2.52 × 10⁻⁹ 15 5.59 × 10⁻⁹7.31 × 10⁻¹⁰ 2.19 × 10⁻⁹ 16 4.78 × 10⁻⁹ 6.24 × 10⁻¹⁰ 1.87 × 10⁻⁹ 17 3.85× 10⁻⁹ 5.03 × 10⁻¹⁰ 1.51 × 10⁻⁹ 18 5.86 × 10⁻⁹ 7.65 × 10⁻¹⁰ 2.30 × 10⁻⁹

As demonstrated in Table 10, the water flux through Samples 13 through18 using deionized water at zero confining stress are similar to theresults for the reinforced NPC alloy composite samples tested in Example6 (salt water, zero confining stress), Example 3 (deionized water, 20kPa and 120 kPa confining stress) and Example 4 (deionized water, 20 kPaconfining stress).

In contrast, the hydraulic conductivity for water through conventionalGCL's is significantly increased as the confining stress is reduced.Moreover, as mentioned in the discussion in Example 6, the salt waterflux through GCL is known to be much greater than 1×10⁻⁸ m³/m²/s.Several conventional GCL's were tested with fresh water in a paper by D.E. Daniel (“Geosynthetic clay liners, part two: hydraulic properties”Geotechnical Fabrics Report 14:5:22; June-July, 1996). At a confiningstress range from 100 to 1000 kPa, conventional GCL's have a hydraulicconductivity range from 3×10⁻¹⁰ to 1×10⁻⁹ cm/s. The hydraulicconductivity increases to a range from 6×10⁻¹⁰ to 6×10⁻⁹ cm/s when theconfining stress ranges from 10 to 100 kPa. Only one data point wasprovided for a confining stress under 10 kPa. The hydraulic conductivitywas 2×10⁻⁹ cm/s for a confining stress of 7 kPa. The data wasextrapolated to show a hydraulic conductivity range of from 6×10⁻⁹ cm/sto about 1×10⁻⁷ cm/s, when the confining stress is decreased to 1 kPa.Accordingly, conventional GCL's have a hydraulic conductivity at least1×10⁻⁷ cm/s or greater, thereby making the composite hydraulicconductivity test results of about 2.5×10⁻⁹ cm/s, at zero confiningstress, particularly surprising and unexpected.

EXAMPLE 6 Salt Water Flux Tests

One problem, among others, with conventional barrier liners, such asGCL, is that their hydraulic barrier properties diminish with exposureto salt water, particularly salt water having a salt concentration about3 wt. % or greater. For example, a conventional GCL has a flux of about1×10⁻⁸ m³/m²/s, using tap water. However, salt water flux through GCL isknown to be much greater than 1×10⁻⁸ m³/m²/s, for example from about1×10⁻⁷ m³/m²/s to about 1×10⁻⁶ m³/m²/s. This example demonstrates how areinforced NPC alloy composite substantially maintains its lowpermeability on exposure to salt water.

Sample Preparation

Samples 19 and 24 were prepared using the following MCX mixture (2:1clay to monomer ratio) applied in the semi-continuous process describedin Example 5:

100.8 g (1.52 wt. %) acrylic acid

400.5 g (6.04 wt. %) acrylamide

55.1 g (0.83 wt. %) NaOH

51.5 g (0.78 wt. %) Na₂CO₃

1.62 g (0.02 wt. %) NBAM

12.8 g (0.19 wt. %) potassium persulfate

1000.8 g (15.09 wt. %) clay

5009.9 g (75.53 wt. %) water

Samples 20 to 23 were prepared using the following MCX mixture (2:1 clayto monomer ratio), which is substantially similar to Samples 19 and 24but in a smaller batch size and applied in a batch type processdescribed below:

50.9 g (1.54 wt. %) acrylic acid

200.5 g (6.05 wt. %) acrylamide

27.55 g (0.83 wt. %) NaOH

25.8 g (0.78 wt. %) Na₂CO₃

0.81 g (0.02 wt. %) NBAM

6.48 g (0.19 wt. %) potassium persulfate

500 g (15.09 wt. %) clay

2502 g (75.50 wt. %) water

Reinforced NPC alloy composites were prepared using the MCX mixturesdescribed above and TERRAFIX® 270R-A geotextile, a non-wovenpolypropylene fiber geotextile, having a thickness of about 2.0-2.5 mm.

For Samples 20-23, a 2 mm thickness MCX mixture was poured onto a 120 mmdiameter piece of the geotextile. A polyethylene film cover sheet wasplaced on top of the MCX mixture and a vacuum pressure in the range offrom about 16 to about 30 kPa was applied to the sample from theopposing side of the geotextile. The MCX mixture was intimatelydistributed in and on the geotextile material by applying the vacuum.The cover sheet reduced channeling through the sample and the MCXmixture was more evenly distributed through the geotextile, as comparedwith a sample prepared without a cover sheet.

The samples were heated using two 320 W infrared lamps (placed about 250mm above the sample) at a temperature of about 80° C. for 10 minutes topolymerize the MCX mixture.

Samples 19 and 24 were similarly prepared. However, the vacuum processwas applied in the semi-continuous process, described in Example 5 andthen passed under the CATA-DYNE™ infrared heater.

Samples were cut into 9.0 cm discs using a high speed drill cutter andweighed. The results are presented in Table 11.

TABLE 11 Weight Unit Weight Sample (g) (kg/m²) 19 13.6 2.14 20 19.063.00 21 15.01 2.36 22 23.26 3.66 23 19.4 3.05 24 15.6 2.45

Hydraulic Conductivity Tests

The hydraulic conductivity tests were based on the ASTM 5887-95 test,described in Example 5.

Flux was tested using two different solutions. The first solution was a3.5 wt. % NaCl solution. The second solution was an artificial seawaterhaving the following composition: 0.46 M NaCl, 0.035 M MgCl₂, 0.028MgSO₄, and 0.01 M KCl. The artificial seawater composition is similar toa natural seawater composition suggested in Introduction to Geochemistry(K. B. Krauskopf, McGraw-Hill, pg. 324; 1967).

The results of the flux tests for the 3.5% NaCl solution and theartificial seawater solution are presented graphically in FIGS. 4 and 5,respectively.

As shown in FIG. 4, the 3.5 wt % NaCl solution's flux through Samples19, 20, 21 and 22 dropped dramatically and rapidly within the first dayof testing. In fact, the first several hours of test results producedthe most dramatic decrease in flux. Accordingly, there are multiple datapoints shown near time zero for these samples. However, the lowest fluxdata points near time zero on the y-axis, in units of m³/m²/s, forsamples 19, 20, 21 and 22 are 1×10⁻⁶, 6×10⁻⁸, 4×10⁻⁷ and 1.5×10⁻⁷,respectively. As a reference point, the dotted line drawn at 1×10⁻⁷m³/m²/s indicates the lowest flux expected from a conventional GCL claybased liner when exposed to a similar salt solution. In fact, manyconventional GCL's are reasonably expected to have a salt water fluxsignificantly greater than 1×10⁻⁷ m³/m²/s, which is at least one orderof magnitude greater than the average salt water flux shown for thecomposite samples of the invention after about 5 days of salt waterexposure. This substantial disparity in the salt water flux performancebetween the conventional GCL compositions and the reinforced NPC alloycomposite is both surprising and unexpected. Without being bound bytheory, it is believed that the unique physicochemical properties of theNPC alloy may provide some synergistic interaction between the clay andnetworked polymer, which, as discussed more fully under Example 7, ispreferably in a naturally hydrated state from date of manufacture andthereby accounts for the composite's precipitous flux drop in the firstseveral hours as well as its at least one, if not two, order ofmagnitude improvement in long term salt water flux performance.

As shown in FIG. 5, the initial seawater flux results, in units ofm³/m²/s, for Samples 23 and 24 are 2×10⁻⁸ and about 2×10⁻⁹,respectively, which are significantly less than for Samples 19-22.Again, as a reference point, the dotted line drawn at 1×10⁻⁷ m³/m²/sindicates the lowest flux expected from a conventional GCL clay basedliner when exposed to a similar salt solution. This substantialdisparity in the seawater flux performance between the conventional GCLcompositions and the reinforced NPC alloy composite is both surprisingand unexpected, for the reasons stated above.

EXAMPLE 7 SEM and X-Ray Analysis

The following SEM micrographs and X-ray analyses illustrate that (1)clay in the NPC alloy is chemically associated with the polymer, (2)clay does not become dissociated from the NPC alloy when the polymer isswollen, (3) NPC alloy is intimately integrated with the reinforcingagent in the reinforced NPC alloy composite, and (4) the reinforced NPCalloy composite can contain a significant amount of occluded waterretained from manufacture.

Monomer/Clay Mixture Preparation

An MCX mixture was prepared as shown in Table 12. The clay used in theMCX mixture was NATURAL GEL™. The monomer was a 1:4 (wt) mixture ofacrylic acid (Aldrich) and acrylamide (Cytec).

Water, NaOH, NaHCO₃, acrylic acid, acrylamide, NBAM and K₂S₂O₈ weremixed in a 10-L HDPE pail. The aqueous solution was mixed well, prior toaddition of clay. Clay was added and mixed again to form a homogeneousMCX mixture. The MCX mixture was viscous but fluid beforepolymerization.

TABLE 12 Component Amount (g) Water 5009.9 NaOH 55.1 NaHCO₃ 51.5 AcrylicAcid 100.8 Acrylamide 400.5 NBAM 1.62 K₂S₂O₈ 12.8 Clay 1000.8 Total (g)6633.02 Clay to Monomer Ratio 2.00 (wt)

Reinforced NPC Alloy Composite Preparation

The MCX mixture was poured in a thickness of about 1.5 mm onto a 0.95m×0.80 m piece of TERRAFIX® 270R-A geotextile, as a reinforcing agent. Apolyethylene cover sheet was placed on top of the MCX mixture and avacuum pressure in a range of from about 16 to about 30 kPa was appliedto the sample from the geotextile's opposing side. The MCX mixture wasintimately distributed in and on the geotextile material by applying thevacuum.

The reinforced MCX mixture sample was put under an infrared heater at80° C. for 8 minutes for polymerization. The moisture content of thereinforced NPC alloy composite was about 75%.

Scanning Electron Microscopy (SEM)

The reinforced NPC alloy composite was examined using a JEOL Model No.JSM 6301 FXV Scanning Electron Microscope (SEM, Japan Electron OpticsLimited, Japan) at the SEM Facility, Department of Earth & AtmosphericSciences, University of Alberta, Edmonton, Alberta, Canada.

Samples were pretreated for SEM examination by placing the samples in aholder and immersing them in liquid nitrogen (i.e., about −196° C.).Once frozen, the samples were removed from the liquid nitrogen, usingpliers or a knife, quickly torn or cut, as indicated below, to obtain across-sectional perspective of the sample. The samples were then quicklytransferred to the SEM vacuum chamber, where they were warmed to −40° C.to sublime any surface ice crystals. Next, the samples were placed in acoating chamber where a thin layer of gold was applied to the sample toincrease electrical conductivity. The samples were then returned to theSEM vacuum chamber for examination. The samples were maintained at ornear liquid nitrogen temperature during the gold coating and subsequentSEM examination. This was done so that the structure of the sample wouldbe preserved. The samples contained considerable moisture and thus hadto be maintained in a frozen state for the SEM to operate properly.

The sample in FIGS. 8 and 9 was cut with a knife prior to mounting. Bothmicrographs show the cut edges of fibers of the reinforcing agent.Particles seen in FIG. 9 are fragments from the cutting step inpreparing the sample for SEM examination. The sample in FIGS. 10 and 11was severed with a pair of pliers, instead of a knife, prior tomounting. FIG. 10 shows the fractured edges of fibers of the reinforcingagent and other fragments produced by fracturing. The SEM micrographs ofFIGS. 6 to 12 are discussed in Table 13.

Discussion of SEM Micrographs

In summary, the SEM micrographs illustrate that (1) clay in the NPCalloy is chemically associated with the polymer, (2) clay does notbecome dissociated from the NPC alloy when the polymer is swollen, (3)NPC alloy is intimately integrated with the reinforcing agent in thereinforced NPC alloy composite and (4) the reinforced NPC alloycomposite can contain a significant amount of occluded water retainedfrom manufacture.

TABLE 13 FIG. # Magnification Description Observations 6 140XComparative. Top plan perspective of reinforcing agent without NPCalloy. 7 7000X Comparative. Potassium acrylate cross- Swollen polymerhas crater-like open-cell structure. The open cells were linked andpolymerized without clay. previously occupied by occluded water, whichwas removed by SEM No reinforcing agent. Sample pre-treatmentprocedures. It is expected that acrylamide/sodium immersed in water for10 minutes acrylate copolymer would behave in a similar manner. prior toSEM. 8 50X Reinforced NPC alloy composite. Illustrates NPC alloyintimately integrated with reinforcing agent. Also Sample dried from theoriginal 75 wt. illustrates thin layer of NPC alloy (right-hand side ofmicrograph) % moisture to about 25-50 wt. % with integrated with NPCalloy in reinforcing agent; i.e., not a laminate structure. ambientdrying conditions over a 2 week period. The NPC alloy shrank around thereinforcing agent fibers. The shrinkage indicates the volume occupied bypreviously occluded water. 9 270X Same as FIG. 8 No individual clayparticles can be seen in the SEM micrographs, illustrating that the clayparticles are chemically associated with polymer in NPC alloy, even atclay to monomer ratio of 2:1. 10 500X Reinforced NPC alloy compositeIllustrates how swollen NPC alloy expands to conform to and immersed inwater for 10 minutes substantially occupy interstitial spaces inreinforcing agent. prior to SEM. 11 4500X Same as FIG. 10. Illustratesthat clay particles are chemically associated with polymer in NPC alloy.No free clay particles are seen, therefore indicating that the clay doesnot dissociate from NPC alloy when water-swollen. Swollen NPC alloy hasopen-cell structure, similar to polymer without clay (FIG. 7). Also, thedegree of occluded water is substantially similar to polymer withoutclay (FIG. 7), therefore indicating that clay even at high loading doesnot have a disproportionately detrimental effect on NPC alloy's swellingcapacity versus a clay-free water absorbing polymer. 12 650XComparative. Same monomer/cross- Swollen polymer fills interstitialspaces in reinforcing agent in same manner linking agent mixture as usedfor FIG. as NPC alloy in FIG. 10. Open-cell structure of polymer without10 sample, but without clay. Immeresed clay similar to that of theclay-based sample shown in FIG. 10. in water for 10 minutes prior toSEM. Comparison to FIG. 10 illustrates how the clay is (a) integrated inthe NPC alloy and (b) does not have a disproportionately detrimentaleffect on NPC alloy's swelling capacity.

As shown more clearly in the comparison between FIG. 10 (reinforced NPCalloy composite) and FIG. 7 (swollen polymer without clay) or FIG. 12(swollen polymer without clay in reinforcing agent), the swollen NPCalloy open-cell structure is similar to that of clay-free polymers.Accordingly, the clay does not constrain the NPC alloy's water swellingcapacity. In view of Ogawa et al (discussed more fully in Example 1),which suggests that clay acts as a cross-linking agent for making waterabsorbent polymers, this is a surprising and unexpected result. Also, inview of the cross-linking agent results in Example 2, which illustratethat a cross-linking agent concentration as low as about 0.1 wt. % canover cross-link a polymer, thereby substantially reducing its waterabsorption capacity, these results are most particularly surprising andunexpected at a relatively high clay to monomer ratio of 2:1.

X-Ray Analyses

The Energy Dispersive X-Ray (EDX) analysis device of the SEM collectssignals from an area of 1 μm×1 μm at a penetration depth of about 1 μm.X-ray analysis was conducted at numerous sites on the sample in FIG. 11,including the NPC alloy at the center of FIG. 11. Consistently at eachsite, peaks appeared for gold (2.1, 8.5 keV), silicon (1.74 keV),aluminum (1.49 keV), sodium (1.04 keV), magnesium (1.25 keV), and iron(0.615, 6.40 keV). The gold peak was a result of the gold treatment forthe SEM examination. The relative strengths and positions of the siliconand aluminum peaks in the EDX spectra were consistent with thoseexpected for bentonite clay. All sites examined showed the presence ofsilicon, aluminum, sodium, magnesium and iron. This analysis shows thatthe NPC alloy is homogeneous throughout the sample, even at the 1 μm³level. Accordingly, the clay in the NPC alloy is chemically associatedwith the polymer.

EXAMPLE 8 Clay Migration Tests

This example illustrates that, when the reinforced NPC alloy compositeis immersed in water, the NPC alloy swells with substantially no clayseparating from the composite.

Reinforced NPC Alloy Composite

An MCX mixture was prepared by mixing 40.51 g acrylic acid with 500 gwater. 36.6 potassium hydroxide and 0.624 g NBAM were then added withstirring. After the potassium hydroxide was in solution, 24.39 gpotassium carbonate was dissolved, followed by addition of 160.33 gacrylamide, 4.83 g potassium persulfate and 500 g water. 594.07 g of themonomer mixture was blended with 199.79 g bentonite clay in a floodblender to give a creamy suspension.

A layer of the MCX mixture was poured onto a 2 cm×2 cm piece ofTERRAFIX® 270R-A geotextile. The MCX mixture was intimately distributedin and on the geotextile material by hand. The MCX mixture waspolymerized in the reinforcing agent by heating in a 75° C. oven for 8minutes.

This reinforced NPC composite was labeled as Sample A in the claymigration tests.

Comparative Sample B—No Polymerization Initiator, No Cross-Linking Agent

The monomer/clay mixture for Comparative Sample B was prepared by mixing18.7 g acrylic acid, 6.1 g sodium hydroxide, 34.9 g clay and 18 g waterto form a viscous paste. The paste was then forced into a 2 cm×2 cmpiece of TERRAFIX® 270R-A. The monomer/clay mixture could not beembedded into the geotextile at 100 kPa. So, one of the inventors,weighing about 80 kg, placed a piece of PLEXIGLAS™ on top of the sampleand stood on it while rocking back and forth. About half of themonomer/clay mixture was forced into the fabric using this method. Nopolymerization initiator or cross-linking agent was added to themonomer/clay mixture.

The sample was dried in an oven at 75° C. for one hour.

Comparative Sample C—No Polymerization Initiator

A monomer/clay mixture was prepared by mixing 79.89 g acrylamide, 20.56g acrylic acid, 0.3 g NBAM as cross-linking agent, 9.995 sodiumhydroxide, 9.962 g sodium carbonate, and 1000 g water. 552.8 g of themonomer mixture was blended with 100.55 g bentonite clay in a floodblender to give a creamy suspension. No polymerization initiator wasadded to the monomer/clay mixture.

A layer of the monomer/clay mixture was poured onto a 2 cm×2 cm piece ofTERRAFIX® 270R-A geotextile. The mixture was intimately distributed inand on the geotextile material by hand. The monomer/clay mixture washeated in a 70° C. oven for 1 hour in the reinforcing agent.

This sample was labeled as Sample C in the clay migration tests.

Comparative Sample D—Pre-Formed Oligomer (MW 2,000)

Comparative Sample D was prepared by mixing 6.5 g pre-formed polyacrylicacid, 1.6 g sodium hydroxide, 26 g water and 10.70 g clay. Thepolyacrylic acid, having a molecular weight of 2,000, was obtained fromAldrich Chemical Co.

A layer of the pre-formed oligomer/clay mixture was poured onto a 2 cm×2cm piece of TERRAFIX® 270R-A geotextile. The pre-formed oligomer/claymixture was intimately distributed in and on the geotextile material byhand. The sample was dried in an oven at 75° C. for one hour.

Comparative Sample E—Pre-Formed Polymer (MW 450,000)

Comparative Sample E was prepared by mixing 4.74 g pre-formedpolyacrylic acid, 1.44 g sodium hydroxide, 96 g water and 11.52 g clay.The polyacrylic acid, having a molecular weight of 450,000, was obtainedfrom Aldrich Chemical Co.

A layer of the pre-formed polymer/clay mixture was poured onto a 2 cm×2cm piece of TERRAFIX® 270R-A geotextile. The mixture was intimatelydistributed in and on the geotextile material using a wooden rollingpin. The sample was dried in an oven at 75° C. for one hour.

Comparative Commercial Products

Two commercial products were also tested for comparative purposes in theclay migration tests.

GUNDSEAL® (GSE Lining Technology, Inc., Houston, Tex.) is a bentoniteclay/polyethylene geomembrane liner. Sodium bentonite is adhered to apolyethylene geomembrane using an adhesive at a loading of 1 lb/ft² (4.9kg/m²). The sample was about 3 mm thick. A 2.5 cm×2.5 cm piece ofGUNDSEAL® was labeled as Comparative Sample F.

BENTOMAT® DN (CETCO, Arlington, Ill.) is a geosynthetic clay linerconsisting of a sodium bentonite layer between two layers of geotextile,which are needle-punched together. A 2.5 cm×2.5 cm piece of BENTOMAT® DNwas labeled as Comparative Sample G.

Clay Migration Test Procedure

Each of the samples was placed in a glass bottle. 100 mL deionized waterat room temperature (about 20° C.) were then poured into the bottle.

The bottle was left standing without disturbance at room temperature.The sample was observed at 3 hours and 22 hours after addition of water,as described in Table 14.

TABLE 14 Sample Description of Sample Observations A MCX mixture:acrylamide, sodium After 3 hours, the sample had swelled acrylate,cross-linking agent, considerably. After 22 hours, there was persulfatepolymerization initiator, some additional swelling of the NPC and clay.alloy. The swelled NPC alloy was puffy in appearance. Both the fabricand clay The MCX mixture was pressed into remained as an integral partof the NPC the fabric and polymerized in a fabric alloy. (see FIGS. 13Aand 13B). @ 75° C. for 8 minutes. Substantially no clay separated fromthe NPC alloy after 22 hours of immersion time. B Comparative.Monomer/clay After 3 hours, the acrylic acid and mixture: acrylic acid,NaOH, water sodium acrylate dissolved in the water. and clay. Nopolymerization initiator The clay had migrated off the fabric and orcross-linking agent was used. swelled at the bottom of the test bottle.The monomer/clay mixture was There was no change after 22 hours. pressedinto a fabric and dried @ 75° C. for one hour. C Comparative.Monomer/clay After 3 hours, the acrylamide and mixture: acrylamide,acrylic acid, sodium acrylate dissolved in the water. NaOH, NBAM(cross-linking agent), The clay had migrated off the fabric and waterand clay. No polymerization dispersed in the water. There was noinitiator was used. change after 22 hours. The monomer/clay mixture waspressed into a fabric and heated for one hour @ 70° C. D Comparative. Apre-formed After 3 hours, the polyacrylic acid polyacrylic acid (MW =2000) was dissolved in the water. The clay mixed with clay and pressedinto the migrated off the fabric and dispersed in fabric. the water.There was no change after 22 hours. (see FIGS. 14A and 14B) EComparative. A pre-formed After 3 hours, the polyacrylic acidpolyacrylic acid (MW = 450,000) was dissolved in the water and some claymixed with clay and pressed into a had migrated off the fabric. After 22fabric. hours, the remaining clay had migrated off the fabric andswelled at the bottom of the bottle. F Comparative. GUNDSEAL ® After 3hours, the clay had migrated off the backing material and started toswell. After 22 hours, the clay was more swollen. G Comparative.BENTOMAT ® DN After 3 hours, the clay had migrated from between the twogeotextile layers and dispersed into the water. The clay had swelled andsettled in the bottom of the bottle by 22 hours. (see FIGS. 15A and 15B)

Line drawings were prepared from some of the photographs taken duringthe clay migration tests summarized in Table 14.

Sample A was a reinforced NPC alloy composite. FIG. 13A illustratesSample A prior to immersion in deionized water. The NPC alloy is in thereinforcing agent 40. FIG. 13B illustrates the sample after 3 hoursimmersion in deionized water. The swelled NPC alloy 46 had a puffyappearance. Substantially no clay separated from the composite. Also,the swelled NPC alloy 46 was still integrated with the reinforcing agent40.

FIG. 14A illustrates Comparative Sample D prior to immersion indeionized water. The pre-formed polymer and clay mixture is in thereinforcing agent 40. FIG. 14B illustrates the sample after 3 hoursimmersion in deionized water. The polymer had dissolved in water and theclay 44 migrated off the reinforcing agent 40 and dispersed in thewater. Some settling of the clay 44 is observed at the bottom of thebottle.

FIG. 15A illustrates Comparative Sample G prior to immersion indeionized water. The sample has clay sandwiched between a firstreinforcing agent 40 and a second reinforcing agent 42. FIG. 15Billustrates the sample after 3 hours immersion in deionized water. Theclay 44 had migrated from between the two reinforcing agent layers 40,42 and dispersed into the water. The clay 44 of Sample G had settledmore densely than the clay of Comparative Sample D, shown in FIG. 14B.

The results in Table 14 and FIG. 13B illustrate how the clay is anintegral part of the NPC alloy. Moreover, the results demonstrate howthe NPC alloy is an integral part of the composite. In all of thecomparative samples, clay migrates from the mixture and/or thereinforcing agent. Also, monomer and pre-formed polymer mixture migratefrom the reinforcing agent. This is shown more clearly in FIGS. 14B and15B.

The reinforced NPC alloy composite remains substantially intact onexposure to deionized water at about 20° C. Specifically, substantiallyno clay separates from the NPC alloy. Moreover, the composite isexpected to exhibit substantially similar performance in deionized waterin a temperature range of about 1° C. to about 60° C. This represents asignificant improvement over the conventional techniques.

EXAMPLE 9 Residual Monomer Content

One concern about using acrylamide as a monomer for preparing an NPCalloy is the leaching of any residual monomer. The FDA limit forleachable acrylamide in polyacrylamide is 0.05% (500 ppm, 500 μg/g) whenthe polyacrylamide is used in treatment of potable water and for paperand paperboard for food contact applications (EPA/600/X-85/270 July1985, PB88-170824).

This example provides residual monomer data for a polymer and an NPCalloy. Generally, the amount of residual monomer is dependent oninitiator concentration, reaction time, and reaction temperature. Forexample, residual monomer content generally decreases with increasedtemperature, increased reaction time and increased initiatorconcentration.

Sample Preparation

A monomer mixture was prepared by mixing 20 g acrylic acid, 80 gacrylamide, 10 g sodium hydroxide, 12 g sodium carbonate, and 0.6 gpotassium persulfate in 1000 mL water. The monomer mixture was dividedinto three parts and NBAM was added as a cross-linking agent at 0.1%,0.3% and 0.9%, by weight, respectively. Each of the three monomermixtures was sub-divided into three parts. Clay was added to some of themixtures in an amount of about 1:1 monomer to clay or about 1:2 monomerto clay, as shown in Table 15. The MCX mixtures were blended in a foodblender to produce a smooth, homogeneous mixture.

Samples of the monomer and MCX mixtures were transferred to plasticbeakers and placed in an 80° C. oven for one hour for polymerization.The samples were removed from the oven and allowed to cool to roomtemperature. The samples were dried at 95° C. for a couple of days.

Residual Monomer Analysis

The residual acrylamide monomer was analyzed by EPA Method 8316 entitled“Acrylonitrile, Acrylamide and Acrolein by High Performance LiquidChromatography (HPLC).”

A weighed sample of dried polymer or polymer/clay alloy (1-2 g) wasplaced in a polyethylene beaker with about 200 mL water and allowed tostand overnight at room temperature (about 20°) overnight. The polymerand NPC alloy samples swelled and absorbed some of the water. Theremaining water was decanted from each swollen polymer and NPC alloy andanalyzed for acrylamide content. The results are presented in Table 15.

TABLE 15 Leached Acrylamide ppm Monomer Mixture Monomer:Clay (μg/gSample (wt.) (wt.) polymer) 25 20% Acrylic Acid, 80% Acrylamide, 0.1%NBAM No Clay 13.1 26 20% Acrylic Acid, 80% Acrylamide, 0.3% NBAM No Clay128 27 20% Acrylic Acid, 80% Acrylamide, 0.9% NBAM No Clay 22 28 20%Acrylic Acid, 80% Acrylamide, 0.3% NBAM 1:1 108 29 20% Acrylic Acid, 80%Acrylamide, 0.9% NBAM 1:1 7596 30 20% Acrylic Acid, 80% Acrylamide, 0.3%NBAM 1:2 90.1

The amount of leached acrylamide, leached by water from the driedpolymer and NPC alloy samples, was well below the FDA limit of 500 ppmfor all samples except one. Sample 29 resulted in a very high leachedacrylamide concentration. Because of the inordinately high residualmonomer, it appears that Sample 29 did not polymerize properly. Thus,Sample 29 is an aberrant data point, especially in view of the Sample 28result, based also on a 1:1 MCX mixture, but with only 108 ppm residualacrylamide, and the Sample 26 result, a clay-free, monomer,cross-linking agent mixture, but with only 128 ppm residual acrylamide.

It was expected that polymerization may not proceed as extensively and,therefore, the amount of leached acrylamide would be greater, forsamples containing clay, especially at higher amounts of clay.Surprisingly, however, as shown in Table 15, the amount of leachedacrylamide was similar for Samples 28 and 30 (0.3% NBAM, 1:1 and 1:2monomer to clay, respectively) and Sample 26 (0.3% NBAM, no clay). It isexpected that the residual monomer contents will be similar forreinforced NPC alloy composite samples.

This and the other examples presented herein demonstrates the advantagesof the reinforced NPC alloy composite over conventional GCL's used influid barrier applications and water absorbency applications.

Preferred compositions and processes for practicing the invention havebeen described. It will be understood that the foregoing is illustrativeonly and that other embodiments of the process for producing areinforced NPC alloy composite can be employed without departing fromthe true scope of the invention defined in the following claims.

What is claimed is:
 1. A reinforced networked polymer/clay alloycomposite comprising a networked polymer/clay alloy, wherein the alloyis a chemically integrated composition of polymer and clay, and thealloy is intimately integrated with a reinforcing agent so that, whenthe composite is immersed in deionized water, at a temperature in arange of from about 20° C. to about 30° C., the alloy swells withsubstantially no clay separating from the composite.
 2. The reinforcednetworked polymer/clay alloy composite of claim 1, wherein thereinforcing agent comprises a substrate having a porous structure. 3.The reinforced networked polymer/clay alloy composite of claim 2,wherein the substrate is selected from the group consisting of knitted,woven and non-woven, natural and synthetic fibers.
 4. The reinforcednetworked polymer/clay alloy composite of claim 3, wherein the syntheticfibers are selected from the group consisting of polypropylene,polyester, polyamide, polyethylene fibers, and combinations thereof. 5.The reinforced networked polymer/clay alloy composite of claim 1,wherein the clay particles in the alloy are swelling clay particlesselected from the group consisting of montmorillonite, saponite,nontronite, laponite, beidellite, iron-saponite, hectorite, sauconite,stevensite, vermiculite and combinations thereof.
 6. The reinforcednetworked polymer/clay alloy composite of claim 1, wherein the clayparticles in the alloy are non-swelling clay particles selected from thegroup consisting of kaolin minerals, serpentine minerals, mica minerals,chlorite minerals, sepiolite, palygorskite, bauxite, silica andcombinations thereof.
 7. The reinforced networked polymer/clay alloycomposite of claim 1, wherein the weight ratio of clay to polymer in thealloy is in a range of from about 0.05:1 to about 19:1.
 8. Thereinforced networked polymer/clay alloy composite of claim 1, whereinthe weight ratio of clay to polymer in the alloy is in a range of fromabout 0.5:1 to about 3:1.
 9. The reinforced networked polymer/clay alloycomposite of claim 1, wherein the polymer of the alloy is a copolymer ofa water-insoluble monomer and a monomer having the following generalformula:

wherein X is selected from the group consisting of OM, OR⁴ and NR⁵R⁶, Mis an alkali or alkaline earth metal ion or NH₄ ⁺, R¹, R², R³, R⁵, R⁶and R⁷ are independently selected from the group consisting of H, CH₃,CH₂CH₃, CH₂CH₂CH₃, CH(CH₃)₂, CH₂CH₂CH₂CH₃, and CN, and OR⁴ is selectedfrom the group consisting of OH, OCH₃, OCH₂CH₃, OCH₂CH₂CH₃, OCH(CH₃)₂,OCH₂CH₂CH₂CH₃, OCH₂CH₂OH and (OCH₂CH₂)_(m)OH, n=0 to about 10 and m=1 toabout
 10. 10. The reinforced networked polymer/clay alloy composite ofclaim 1, wherein the alloy is formed by exposure to an energy sourceselected from the group consisting of thermal energy, electromagneticradiation having a wavelength less than about 10 nm and combinationsthereof.
 11. The reinforced networked polymer/clay alloy composite ofclaim 1, further comprising a substantially non-porous layer.
 12. Thereinforced networked polymer/clay alloy composite of claim 11, whereinthe substantially non-porous layer is selected from the group consistingof HDPE, PVC, VFPE, fPP, CSPE, and combinations thereof.
 13. Thereinforced networked polymer/clay alloy composite of claim 1, whereinthe moisture content is in a range of from about 25 to about 75% byweight.
 14. The reinforced networked polymer/clay alloy composite ofclaim 1, wherein the residual monomer content is less than 200 ppm byweight of the polymer in the alloy.
 15. The reinforced networkedpolymer/clay alloy composite of claim 1, wherein, when placed under azero confining stress, the flux with deionized water is less than about1×10⁻⁸ m³/m²/s.
 16. The reinforced networked polymer/clay alloycomposite of claim 1, wherein, when placed under a zero confiningstress, the flux with a 3.5 wt. % NaCl solution is less than about1×10⁻⁸ m³/m²/s.
 17. The method of using the reinforced networkedpolymer/clay alloy composite of claim 1 as a fluid barrier in aconfining stress range of from about 0 kPa to about 10000 kPa, wherein,when placed under a zero confining stress, the barrier has a deionizedwater flux less than about 1×10⁻⁸ m³/m²/s.
 18. The method of using thereinforced networked polymer/clay alloy composite of claim 1 as anabsorbent material used in a personal care article.